The Big Bang Theory discrepancies - the sitcom's, not the other big bang

Are you a fan of the big bang theory sitcom?
How big a fan ? enough be interested in a comic-con panel ?

then maybe you will also be interested to read about the discrepancies I have been spotting in this show over the years.... spoiler alert: if you didn't watch the whole series till the relevant chapter, you will encounter spoilers!

Let us begin with a small bit:
A series-long issue that just doesn't stand to reason. How can penny afford living alone, while Leonard and Sheldon have to be roommates ? they live in the same building!
(think of the number of rooms + and recall that chapter when Sheldon tells Leonard "frankly, if i could afford the rent, i would throw you out" (it was season 1, episode 7; from now episodes shall be shortened to s for season, e for episode, combined with numbers making the format sXXeYY, and shortening that footnote into s01e07).

Before moving into a season-by-season detail, let us set some ground rules. We will only be judgmental to issues not holding together since season 3. Seasons 1&2 are not judged, because things were still finding themselves. Even basics, as since when did Sheldon and Leonard start living together changed between seasons 1 & 3; on s01e07, Sheldon tells Leonard that ever since they moved into the apartment, he watched Dr. Who on saturday morning; But on s03e22, we are told that Leonard moved into an apartment Sheldon was already living in. Not convinced? Consider Sheldon -

• He was not always as arrogant; 
• the roommate agreement did not manifest itself; 
• Sheldon was actually noticing girls (Consider s01e07 for example. Remember Sheldon complaining that it cannot be that someone can be so pretty and good at video games as penny was in that episode? )
• Sheldon did not insist on no-one sitting at his place (Compare s02e02 to s01e07 to see the inconsistent evolution of this concept) 

(for those who insisted, see the addendum-post: seasons 1&2 discrepancies)

Now, let us begin with the season-by-season discrepancy list:

1. s03e03: Sheldon states - "Penny, while I subscribe to the many worlds theory which posits the existence of an infinite number of Sheldons in an infinite number of universes, I assure you that in none of them am I dancing." But this stands in contradiction to s04.e21 where sheldon tells Penny, Bernadette and Amy:"for the record, I’m an excellent dancer. Proficient in the rumba, waltz and cha-cha. " wonders "I don’t see why that’s surprising. I excel at so many things. You’ve had my sourdough bread." and explains that he took dance lessons "Against my will. In the South, pre-adolescent children are forced through a process called cotillion, which indoctrinates them with all the social graces and dance skills needed to function in 18th century Vienna."
2. s03.e09: Penny says she told Bernadette some bad things about Howard, and yet, on s04e04 it turns out she never told her the real sassy bits...
3. s03. e18: Sheldon the germophobe drinks alcohol out of glasses of other people, who have already drunk a little from them !!!
4. s04.e10: Bernadette says that Howard gives her jewlery after every time they dine with his mother; and yet, on s04.e23 Bernadette and Howard's mom eat together for the first time, to get to know each other following the engagement.
5. s04.e14: Howard says about Sheldon's disappointed response to students disliking his teaching style, "i think that is what Darth Vader said before he started building the death star", only Darth Vader never built the death star and any self-respecting geek show know that.
6. s04e17: Sheldon tries ordering pizza on thursday night from a place called "Luigi", in a process which seems like a first-time order. but on s04e21 , on pizza night, it is declared that originally they ordered pizza from Franconi, according to the roommates agreement, and after he went out of business they switched to Grazziano (which is revealed to be against the rules, as Priya tells the guys)
8. s04e21: Penny asks Sheldon if he had ever kissed a girl. He replies "Other than my mother, my sister and my mee-maw, no. But in the interest of full disclosure, I was once on a bus and had to give mouth-to-mouth resuscitation to an elderly nun who passed out from heat exhaustion. Every year I get a Christmas card from her, signed with far too many X’s and O’s."
   but on s03e10 Leonard's mother kissed Sheldon (and afterwards said she'd rather have the busboy).
9. s04.e22 Priya and Leonard talk about a summer trip to India; s04.e24 Priya plans to get back to india and does not tell Leonard who accidentally hears about it when she and her parents video-chat.
10. s04.e24 Priya says she can't believe she wears her brother's Halloween costume. Leonard says he can't believe she thinks he wears it only on Halloween. but on s04e18 Priya talked of the outfit with knowledge, as a great source of pain to the family... (and also on s04.e23 talked with penny about the days in which raj was in a group of friends which dressed like the power rangers - so why all of a sudden this ignorance regarding his costume habits?)
11. s05e12: Howard tells Bernadette he started doing magic when he was a teenager. whereas in s06e07 (the "The Habitation Configuration" when Howard is actually moving out) Howard says he tried cheering his mom up after his father left (he was only 11 then).
12. s05e12: Bernadette says she is not good with kids and hates kids cause her mom worked full time and she had to watch younger brothers and sisters. whereas in s03e14 she said her mother had an illegal daycare and therefore she "knows how to deal with stubborn children" (having performed the magic of being able to send sleepless Sheldon to bed).
13. s05e15: Sheldon and Leonard stop being companions following Leonard's choice to go home after a white night at work, instead of remaining all day, to take Sheldon to the dentist in the afternoon. Sheldon arrives late to the apartment has dinner with everyone, and the following day is visiting Stuart's shop, seeking a ride to the dentist. talk about an editing blunder.
14. s05e05: Howard tells his gf that he wants to take a one man submarine to explore the depths of the ocean but at s04e04 he said that having taken a scuba diving course he found out he is terrified by the ocean....(we could mention Bernadette's telling how howard got sea sick on pirates of the Caribbean.... ); one should say that this particular discrepancy might be solved/explained by referring to Howard's words as daydreaming/bragging... 
15. s05.e17 Kripke and Sheldon are left at the restroom after president Siebert left. Kripke takes the urinal to the right and starts when Sheldon tells him "you are in my spot", but in s02e15 Sheldon agreed with Beverley (Leonard's mom) that "In bladder voiding, as in real estate, it’s location, location, location." . Although not decisive, it is implied that Sheldon agrees that the central urinal is the right choice , just like Leonard's mother prefers it (yes, it could be that he agrees to the principle of "the right urinal" but has other preferences. Have you known Sheldon so far to be the one who respects other people's preferences and choices when he has formed an opinion ?)
16. s05e15: During another of the lapses in friendship (this time because of one night drill too many), Sheldon tries to interest the other friends in driving him around and mentions, among other transport needs, that he needs to be taken to Supercuts. but in s05e18 he tells Amy that he tried Supercuts and discovered that "They do men’s and women’s hair in the same room at the same time. It’s like Sodom and Gomorrah with mousse."
17. s05e21: a critique's voice: no bachelorette party? REALLY? ?!? do us a chauvinist favor. We expect better from the characters of Amy and Penny. 
18. s05e24: Penny knows people who were married in Vegas and suggests the option to Howard and Bernadette but in s07e09 she recalls her lovely thanksgiving day with Zack in Vegas when they did one of those fake weddings?
19. s06e04: Sheldon can't swim because he has a higher than average body density... but in s02e13 it is mentioned that he has learned swimming by reading a "teach yourself to swim guide" and therefore does not need to attempt it in real life. Is it personal growth ? something that he discovered in the out-of-screen events taking place between the seasons ? or a plain discrepancy?
20. s06.e04: Amy states that she finds the idea of dressing in matching costumes for a costumes party is one of the opportunities of proving your boyfriend is not imaginary and appears to have been looking forward to such an event. But in s04.e11 (in the dialogue where penny is persuaded to wear wonder woman's costume for the new year eve competition in the comics store)  Sheldon states that Amy is not as free spirited as him, and does not believe in wearing costumes.  
21. s06e08: Sheldon describes Leonard as a good sleeper. A real catch compared to a guy who snores. And yet, on s08e09 he describes Leonard as snoring since he had met him....
22. s06e09: Amy says that the battle over the parking spot between Howard and Sheldon couldn't be avoided because of them being two testosterone-fueled alpha males. But in s06e06 she got excited with Sheldon's potential victory over Steven Hawking (which never happened) because she thought it might give him a testosterone level...
23. s06e11: We see the guys play D&D. they get to a room with a chest,try to open it, and then the walls start closing in, and only Sheldon's singing of Good King Wenceslas stops the walls. The scene is cut mid-song to another scene with the girls, and returns to Sheldon finishing his song. But then the D&D game continues with Leonard saying "you leave the room and find yourself in front of a melting snowman." What happened to the chest? why do they leave the room upon the Dungeon Master's order and not upon their own choice?  Horrible D&D continuity.
24. s06.e20: Leonard says his mother would be proud if he got tenure at cal-tech, but at s02e15 his mother said about achievements of related persons "it her achievement, not mine, why should i be proud?" ... He should have known better...
    This discrepancy occurs again at s08e23. Then, she is proud of another son (arguing before the supreme court). Why this is worthy, but her daughter's scientific achievement wasn't ? (the daughter grew a human pancreas in a gibbon, for god's sake, but all Beverly had to say back then was "it's her achievement, not mine, why should i be proud?"
    And yet, about the re-occurrence, one might claim it is personal-growth for Beverley... 
25. s07e05: Sheldon says he always interpreted "don't defecate where you eat" literally and that is why he never did that in any restaurant he ate, but he has been known to -
    1) speak about location location location to Leonard's mother (but he might be referring to peeing);
    2) go to the restroom in s05e04 (the D&D style dice rolling, decision making protocol) (but once again, it might be for peeing);
    3) has a very specific restroom schedule Leonard describes in s06e08 (the wormhole generator hoax chapter).
    but the decisive discrepancy argument: let us not forget the 1 hour it took Sheldon on s05e16, because of the time that it takes him in a new place.... 
26. s07e15: Penny responds to Leonard's suggestion that they have sex on Sheldon's spot (Valentine's day and Sheldon and Amy are away), with "that is the least sexy thing anyone has ever said to me", but on s03e04, she suggested that they make out on Sheldon's spot... (is it a true discrepancy, or has penny embraced Sheldon's code?)
27. s07e15: Leonard and Penny have been for a while in Leonard's room for Valentine's day sex. Later they argue  whether 9 minutes is a while, or 30 minutes is a while (the sex took the shorter time). but in s04e23 Leonard described himself as king of foreplay (and this was verified by Penny telling Priya he tries so hard, she actually fell asleep during foreplay).
28. s08e05: the girls go to Vegas after checking about flights, but in s06e23 Amy was put on the no flights list.
29. s08e08: Leonard tells Penny she would never had hit on him in prom because it was before his growth spurt.... but in s01e09 he told her his last growth spurt was in the eighth grade!
30. s0820: Leonard suddenly has no money ? living a prudent life (with the exception of spending money on toys) for 8 consecutive seasons? living with a roommate at age 30 ? considering all the money Shledon has been keeping ? yes, we all know this was a premise of the pilot chapter, but that was 8 seasons ago, and since s01e01, the premise was that our nerdy heroes are doing quite well. And btw, Leonard could earn half of what penny does without being poor.
31. s08e24: Leonard have not told Penny about making out with someone during his s07e01 north sea expedition? really ?!? that is so out of his character. totally un-Leonard not to torture himself with it during s07 and come out with the truth after 3 episodes... completely out of character. horrible scripting move, which stands in line with some other season 8 blunders.
    But wait. This could be considered as a wider discrepancy by the more critical. They would claim it is also an out-of-character moment for Penny. Remember Penny at s05e22? she was so confident that she has nothing to worry about Leonard going to Howard's bachelor party (sleazy Howard Wolowitz!) and she gets worried ? (But the more lenient would suggest that now that Penny has lowered her defenses, she is worried about Leonard; It might also be that having seen other women interested in Leonard (remember Alex?) she knows it is not far fetched as she used to think. It might also be that with her self esteem gone low she doesn't evaluate Leonard's devotion to her as in the past. And one last option - she might know that he is no longer his former shyness ....) 
32. s09e02 Howard knows how much marriage Counseling costs. Raj is surprised. But in s08e09 it was told that Raj and Howard went to couple's counseling together (back then, btw, Bernadette did not know about it at all.
33. s09e3: Penny is sure that deceased Moondance, penny's late hog, was buried in the yard and does not agree to the idea that her family would eat a beloved pet. But on s07e22 (Arthur's funeral) she told about her former experience with death, when her former pet pig died. "I had a pet pig when I was a kid. I mean, when he died, we didn't have a funeral, we had a barbecue." 
34. s09e09: what happened to the tradition of a thanksgiving meal Sheldon was nagging about so much in s07e09?
35. s09e09: Penny not remembering Leonard's birthday is totally out of character. Is it logical that the girl who kept every nostalgic item of their relationship (s07e06) and who especially arranged a surprise party back when her acquaintance with Howard was in early infancy (s01e16) because he never had birthday parties celebrated before will forget her spouses birthday?
36. s09e09: Penny telling Sheldon she never remained a friend with any of her ex-boyfriends, while we all remember season 4 and the relevant bits from 3 & 5 .... (also her wedding vows, when she told leonard he is her best friend).
37. s09e15: Rajesh asks the friends (who mock him), if any of them ever broke up a relationship with anyone, and they remain speechless, and no one mentions:
    1) leonard breaking up with dr. Stephanie Barnett (s02e10);
    2) sheldon breaking up with the Ramona Lewitzki (s02e06);
    3) leonard breaking up with Pryia (s05e07).
38. s09e20: playing the drinking game "never have i ever", Sheldon tells he has been arrested but only for j-walking. But what about that time on s02e16 when Sheldon insisted on not paying a traffic ticket, insulted a judge and was arrested? (Penny was there! and yet, neither Sheldon nor Penny remember it....)
39. s10e04: Leonard, troubled by the forming friendship  between Penny and his mother, tells her he married her to hurt his mother, which might be nice as a joke for the chapter, but contradicts Leonard's anxious will to please his mother, and his fear from his mother's opinion about Penny as a girlfriend, back in s03e11. 
40. s10e05: Amy has difficulties adjusting to Sheldon's bathroom schedule, and yet, on s07e16 she responded to Sheldon's telling of the difficulties he had in training Leonard to a bathroom schedule with empathy to Shledon's difficulties (she described Leonard's prior bathroom habits with the sentence - "like a dog boy"). One would expect that she too, would have strict habits, similar to Sheldon's. 
41. s10e10: Sheldon tells Leonard he never beat him in 3d chess (as an excuse why Sheldon should take the set to his apartment as the roommates finally separate). But on s05e23, Leonard was winning,before the two stopped the game to "bellyaching about their ol’ ladies".
42. s11e08: Sheldon (while arguing with Amy about his adison/tesla behaviour regarding the army project) states that he does not know any neurologist name other than amy.... but we all remember the Babinski defecates Maxwell argument from s04e03(Joseph Babinski is a french neurologist best known for the decription of the babinski sign, a reflex elicited when the sole of the foot is stimulated with a blunt instrumen). 

Wow.... that was a rather long list of discrepancies for a series that deals with science, wouldn't you say?

Have any other discrepancy you wish to add? Don't agree with an item? feel free to talk back or write to me.

Addendum 1: How did Leonard get Penny ? 
Before we depart, let us discuss another annoying issue. Maybe not exactly a discrepancy, but definitely a bad call by the script writers.
In season 8 there is this notion that Leonard got Penny by begging (s08e07, with Dr. Lorvis)/
by making her feel sorry for himself (leonard saying so himself on s08e19). But this is completely
inconsistent with the way the series played out (Penny realizing by s04's end that Leonard
is a great guy and she messed up with him; Leonard growing confident enough to suggest
they start going together again during s05e13). Whatever the others might be saying to
break Leonard's balls, there is just no way in the world that he will say it about himself.
he knows he earned it.

Addendum 2: Sheldon's driving 
Sheldon's driving has knowing some highs and lows. Not all consistent with each other...

• s02e05: Sheldon is forced by the others (uncharacteristically) to get a driving learner's permit. But he is unable to learn to drive, displaying horrible skills on a simulator. 
• s03e08: Sheldon drives Penny to the hospital as she had dislocated her shoulder and no one else can help. 
• s03e22: Sheldon says that he can drive but prefers not to.
• s08e12: Sheldon tells Leonard that Amy has taught him how to drive. That he avoids
  it because he is afraid and sometimes gets the pedals mixed up. But more impoprtantly,
  driving Sheldon to work is one of the things that give purpose to Leonard's life.
• s10e16: Sheldon tells Amy he got his driver's license two years ago, but that he lets her chauffeur him to let her feel important.
• s11e04: Sheldon tells Howard he has a license for 3 years, but that -
   1) he barely passed the test
   2) the only time he drove, he made a u turn, got dizzy, threw up and walked home.
  at the end of that chapter, btw, Sheldon, getting confident as a driver thanks to Howard's fatherly style of guiding him,  gets stopped by a cop for speeding. Sheldon hands the cop his license and tells him that he won't be needing it anymore. 

Addendum 3: Some useful resources

• The entire scripts of the series on bigbangtrans.wordpress.com
• The Big Bang Theory wikia
• Ever tried searching the internet and ran into Big Bang Cultural impacts? try it....

[update: 16/07/2017:  the addendum-post: seasons 1&2 discrepancies has been published!]
[updated: 31/10/2017; updated addendum 2]

[updated: 1/12/2017; added item 42 on the list of discrepancies]