Top 20 Big Bang Theory Plot Holes You Didn't Notice

#20: When’s Sheldon’s Birthday?

We could probably make a whole list of characters who seem to celebrate their birthdays more than once a year, and Sheldon would be on it. While discussing Leonard’s birthday, Sheldon goes on one of his rants, and Penny responds. If, like Penny, you read horoscopes, you’d know that would place his birthday between April 20th and May 20th. Then in “The Intimacy Acceleration,” Penny learns that it’s Sheldon’s birthday that very day. Now he’s a Pisces, is he? So, was Penny just making an assumption the first time? We know Sheldon hates birthdays, but given his track record on secret keeping, we doubt he lied about the real date all those years ago.

#19: How Long Did Leonard & Joyce Kim Date?

You remember Joyce Kim, don’t you? She was Leonard’s girlfriend for almost a month. Or a matter of hours. That depends on which episode you’re watching. Leonard’s brought up his former fling a number of times, beginning with the pilot. When the guys discuss his relationship with Dr. Stephanie, Howard mentions Leonard and Joyce Kim were together for 27 days, with Raj confirming a detail from the pilot. However, in “The Staircase Implementation,” we meet Joyce Kim only about 12 hours after Leonard apparently did. He admits Sheldon’s lack of social skills saved him from revealing confidential information. But surely he didn’t keep dating her after discovering the truth? Or kept things long-distance after she defected?

#18: Sheldon’s Dad Looks a Lot Like a Jerk from Leonard’s Past

Look, we know the “BBT” creators hadn’t yet cast or perhaps even conceived “Young Sheldon” when they cast Lance Barber as Jimmy Speckerman, an unwelcome blast from Leonard’s past. However, we’re not here to discuss the real world, and many “TBBT” fans have called out this choice of double-casting, too. Wouldn’t Sheldon be spooked that the guy who used to torment his buddy looks like his dad? Barber reprised his role as George Cooper on the parent series in the videotape that encourages Sheldon not to lose hope. Perhaps he was too focused on his dad’s words to think, “Hey, doesn’t dad look a whole lot like that Speckerman guy I met a while back?”

#17: Does Sheldon Dance?

Who can resist the captivating earworm that is Shania Twain’s “Man! I Feel Like A Woman!”? Sheldon, apparently. Even in his “many worlds” theory, it seems that in none of them does that catchy beat manage to draw so much as a head bop out of him. We’d totally believe that, except we later learn he was forced into cotillion lessons as a kid, although we're sure he hated every second. We’ve also seen him take a salsa class with his friends and cha-cha with Amy. There was even the time he tried to use Flamenco to seduce her. So maybe other world Sheldons don’t dance, but this world’s Sheldon is surprisingly quite the mover.

#16: Are Raj & Neil DeGrasse Tyson Friends or Foes?

The famous astrophysicist first appears in season four, where Sheldon has beef with him, but he seems to be on good terms with Raj. Yet when Raj gets invited to appear on a local news channel to discuss an impending meteor shower just a few years later, he derails the interview with some jabs at Tyson. He then takes this feud online, clearly letting his 15 minutes of fame get to his head. Why is he riling up a man with whom he had a good relationship and should probably stay on the right side of? We wonder if they went back to friendly professionalism after Tyson threatened him with a DeGrasse kicking.

#15: Where Was Leonard During the Summer of 2009?

If we take ourselves back to the end of season two, the guys were headed out on an expedition to the Arctic. It’s a once-in-a-lifetime opportunity and one you’d be unlikely to forget, right? Well, if we fast forward to season five in 2011, Leonard shows a woman a sketch of him from Comic-Con dressed as Lion-O from The Thundercats. He claims he’s had it since, yep - you got it - the summer of 2009. Now we doubt that Leonard mastered time travel, but if you do the math, it’s hard to fathom how he could have possibly have been in two places at once.

#14: Where Is Penny’s Sister?

Penny’s ever-changing family is a bit of a mystery. For instance, she doesn’t seem to know her own father’s name, first naming him as Bob despite his later introducing himself as Wyatt. We also learn she has a sister named Lisa that we never meet. Here’s what we do know about Lisa: her water broke at her own wedding, she shot her husband when they were both drunk and she gave Penny a bikini wax using crayons when they were younger. However, not only does Lisa not attend her own sister’s wedding but no one in the family even mentions her - which begs the question, where is and what happened to Lisa?

#13: Penny’s Career Path

When we first meet Penny, she’s an actress/waitress struggling to make ends meet. Luckily, it’s Bernadette to the rescue when she gets Penny an interview at her firm to be a pharmaceutical sales rep in season 8. The only problem is that Penny has no qualifications or medical background. Yes, it is more sales than medical know-how, but even if companies let that stuff slide, would they be willing to take a risk and hire someone with such a limited educational background? Don’t get us wrong; we’re glad that Penny’s luck changed - but was their boss really that so scared of Bernadette that he was willing to overlook all of this?

#12: Did Howard Move Out for MIT?

Until Howard moved in with Bernadette, one of the series’ biggest running gags was that he still lived with his mother. It’s often implied that he never left his childhood home. Only, didn’t he go to MIT? Or, to use its full name, the Massachusetts Institute of Technology? Given this would’ve been in the late ’90s to early ’00s, remote learning probably wasn’t an option yet. An undergraduate and master’s degree would take around five years to complete, so was he living in Massachusetts that whole time? If so, why do we have a sneaky suspicion his mom moved in with him? We don’t think her bubbala could survive all those all-nighters without her cooking!

#11: Can Raj Speak Hindi or Not?

Hindi is the most widely spoken language in Raj’s native India, yet he tells Sheldon that he never learned to speak it. Only that’s not entirely true, is it? For one thing, he clearly understands enough to listen to the radio. He also knows enough to slip certain Hindi phrases into conversation. We also know he’s a fan of Bollywood movies, though sure, he could always rely on subtitles for those. Yet perhaps the biggest clue that Raj knows more Hindi than he lets on comes when he’s watching cricket with Ruchi. When she comments on the game in Hindi, from what we can tell, he serves as an excellent translator.

#10: When Did Leonard & Sheldon Meet?

As the guys plan their trip to see “Raiders” with an exhilarating extra 21 seconds of footage, Sheldon remembers waiting 14 hours in line with Leonard for the midnight premiere of “Star Trek: Nemesis.” Hold on just a moment, that would be illogical! According to “The Staircase Implementation,” they met in 2003, but any real Trekkie knows “Nemesis” came out in 2002. You’d think Sheldon would remember details like this! Or did that time-travel clause in the roommate agreement miraculously come into play or something? And while we’re on the topic of wonky memories, Raj claims he started straightening his hair after meeting Howard. Yet, in the flashback, Howard’s hair is definitely not straight.

#9: Sheldon Doesn’t Remember When His Dad Passed

Sheldon tells Bernadette’s dad that he lost his own father when he was 14. That was later confirmed in “Young Sheldon,” too. But back in season one, he also talks about the time his mom had to fly back from Germany to help his dad after a storm. When he was 15. Now, we’re not here to nitpick all the “Young Sheldon” inconsistencies; that’s a whole other list, but we do want to focus on this: he says it happened when he was 15. Given what we know, that’s kind of impossible. Sheldon loves to brag about his flawless memory, so you’d think he could keep his timelines straight, right?

#8: Bernadette’s Super Long Pregnancy

It’s a happy Valentine’s Day in the Rostenkowski-Wolowitz home when Bernadette announces she’s pregnant - but only to the injured rabbit she and Howard found in the hot tub. Now fast forward to December when their bundle of joy enters the world. Hang on, what!? If Bernadette knew she was pregnant in February, then we have to assume she’s at least a month into her pregnancy. This would mean they conceived Halley in January and come December, it would mean she’d been pregnant for 11 months. Now, we’re no experts, but we’re pretty certain that’s a longer than average pregnancy! It must have been super uncomfortable as well - poor Bernie!

#7: Sheldon’s Cat Allergies

Early on in the series, we find out that Sheldon is allergic to cats or that they’re likely to set off his asthma (although isn’t Leonard the asthmatic one?). However, when Sheldon and Amy part ways in season 4, Sheldon decides to get a cat as his new companion. When he worries that his furry new friend will be lonely, he gets a whole clowder. But there are no symptoms of an allergy to be seen during this time - not a sneeze or even a sniffly nose. This was clearly an oversight by the writers, but since those cats are just so darn cute, we’ll let it slide.

#6: Raj Talks in Front of Penny

Raj’s selective mutism was a running gag for many seasons and alcohol was the only temporary cure. However, in an early episode during which Howard is entertaining a lady, the others discuss how to proceed with game night without him. Leonard jokes about splitting Raj in half, Raj fires a comeback, and it seems he’s forgotten that Penny’s there. There’s no alcohol around and no one says a word about it, so either he’s suddenly and temporarily gotten really comfortable around her - or the writers momentarily forgot about his condition. We’ll let you be the judge.

#5: Howard Couldn’t Have Gone to Space

It was an exciting time for Howard when he was selected to go into space. We don’t want to be a Sheldon about this, but in reality it would never have happened. For starters, he has too many health issues. But even if we put a pin in all that for now, there’s also the fact that he barely made it through NASA’s intense training, even getting his mother and fiancee to come take care of him. Despite all this though, real life NASA astronaut and “Big Bang Theory” guest star Mike Massimino, praised the set’s attention to accuracy during their characters’ time in space, so at least there’s that.

#4: Breaching The Roommate Agreement

We know that Sheldon is a stickler for the rules and loves a good contract, so you’d think he’d do a better job at ensuring the roommate agreement is heeded to. Both he and Leonard have actually broken the agreement, but these times have seemingly gone unnoticed. For instance, Leonard has had lady friends stay over without giving the 12 hours notice, which Sheldon never even mentions. And we already talked about Sheldon’s clowder, despite the contract saying no pets, with very limited exceptions. For someone who claims to have an eidetic memory, he sure forgets things when it’s convenient.

#3: Sheldon’s Three Knocks

We don’t learn about the origins of Sheldon’s compulsive habit until season 10. From what we know, he’s been keeping up with his three knocks ever since. Yet, back in early season one, the writers hadn’t yet developed this knock, as we can see here. In fact, the first time we see him do his signature three is in “The Loobenfeld Decay,” and he pretty much does it ever since. We get it; it was early days, and the characters are still being developed. Still, considering what a huge ritual this becomes, it’s harder to go back and not feel like something is missing when he only knocks the regular amount on Penny’s door.

#2: When Did the Elevator Break?

Fans did get to see the elevator repaired by the end of the series, but what we still want to know is when exactly it broke in the first place! Leonard tells Penny about how it broke, dating it back to 2003. But in season one, Leonard says in 2008 that it’s been broken for two years - dating the break to 2006. Moreover, Howard is seen checking out the broken elevator as if he doesn’t know how it broke, even though a flashback shows that he was actually present and very much involved in the incident. Very strange indeed.

#1: Sheldon’s Spot

As any Big Bang fan can tell you, no one but Sheldon is allowed to sit in Sheldon’s spot - and if you dared to try, that’s not a mistake you’d be likely to repeat. Occasionally, we do see some of the others sitting in the sacred spot and conveniently, Sheldon doesn’t say a word. Now we know Sheldon isn’t the kind to let things slide. It also seems unlikely that Sheldon will quietly sit elsewhere if someone else just happens to be in his spot. After all, he did call “eternal dibs.” Although, isn’t it curious that he has a spot in a jail cell he’s never been to, but not in the university cafeteria?

What’s a plot inconsistency you noticed? Let us know in the comments