The Big Bang Theory: 25 Glaring Plot Holes We Can’t Unsee

The Big Bang Theory has been a big hit since it came on the air in 2007. The show has dealt with the misadventures of four friends, Leonard, Sheldon, Howard, and Raj, whose lives are changed when they meet Sheldon and Leonard's new neighbor named Penny. The Big Bang Theory is currently in its twelfth and final season, but the series has so far provided eleven seasons worth of laughs on CBS.

The characters on the show are not only incredibly intelligent scientists, but they are also big comic-book nerds, which has provided several fun cameos and storylines as the series progressed. While the show has struggled with ratings every now and again, the show has done well enough at CBS to warrant a spinoff series called Young Sheldon, which focuses on the early years of Sheldon Cooper.

Over the last twelve seasons, the characters on the show have each gone through elaborate character arcs, which have also opened the door for serious plot holes. Most TV shows and movies are bound to have a few plot holes here and there, but The Big Bang Theory has some plot holes so big that fans can’s unsee them.

With that said, here are the 25 Glaring Plot Holes In The Big Bang Theory We Can’t Unsee.

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25 Is Sheldon A Pisces Or A Taurus?

The Big Bang Theory might not focus on the exact dates that each character was born on, but the show did create a plot hole based on Sheldon Cooper’s birthday. Sheldon was born inside of a Walmart with his twin sister Missy on February 26, 1980. In the sixteenth episode of the first season titled “The Peanut Reaction”, Sheldon explains why horoscopes are fake, to which Penny replies, “Blah blah blah, typical Taurus.

Being a Taurus would mean that Sheldon was born sometime between April 20th and May 20th, but of course that’s not the case. In season 8, Penny then correctly calls him a Pisces, but that doesn’t correct the plot hole that was made in season 1. 

24 Sheldon’s Spot

The Big Bang Theory Couch

Sheldon has many odd quirks on The Big Bang Theory, but one thing that most fans know is that he is very particular about his spot on the couch. Sheldon has claimed eternal dibs on the left side of the couch for a variety of reasons, but mainly because it is a “single point of consistency in an ever-changing world.

Sheldon becomes quite irritable when others sit in his spot, but only sometimes. Several times other characters sit in his spot and Sheldon doesn’t seem to care, but other times he gets very angry about his spot. 

23 When Was The Elevator Broken?

Leonard, Penny and the Broken Elevator in The Big Bang Theory

One of the ongoing gags on The Big Bang Theory revolves around the gang’s elevator being broken. The elevator is said to have been broken for two years in the episode “The Nerdvana Annihilation” in season 1. However, in season 3 during the episode “The Staircase Implementation”, it is explained that the elevator broke when one of Leonard’s experiments went wrong.

This created a plot hole about how many years the elevator has been broken, but it gets even worse. In later seasons, Howard is seen trying to solve the mystery of the broken elevator, even though he was present when Leonard's experiment went wrong. 

22 Leonard And Joyce’s Relationship

Leonard and Penny may have ended up getting married later on in The Big Bang Theory, but she was hardly Leonard’s first girlfriend. One relationship Leonard had was with a character named Joyce Kim, played by Ally Maki. In the episode “The Staircase Implementation”, Leonard mentions that he only knew Joyce Kim for 12 hours before Sheldon finds out she is a spy from North Korea.

In a previous episode, “The White Asparagus Triangulation”, it was mentioned that Leonard and Kim were together for 27 days. While it may not seem like a big plot hole, being together with someone for half a day versus more than a month is a pretty big difference.

21 They Don’t Recognize Eliza Dushku

Eliza Dushku in The Big Bang Theory

One of the most interesting aspects of The Big Bang Theory involves the guest stars who make it into the show. Since the gang is not only incredibly smart, but also pop culture savy, the four friends have many interests in movies, TV shows, and video games. One TV show that is mentioned several times is Buffy the Vampire Slayer.

It is well-known that the friends are fans of the show, but when actress Eliza Dushku, an actress on Buffy, appears in season 4 as an FBI agent, nobody recognizes her. Surely they would have recognized her, especially since they recognize other pop culture icons who appear on the show.

20 Penny Doesn't Know Her Dad’s Name

Penny's Dad in The Big Bang Theory

For the entire series, Penny’s last name has remained a mystery. Her last name is currently Hofstadter since she married Leonard, but it appears that her father’s first name is still a mystery as well. In the episode “The Maternal Congruence” when Leonard’s mom comes to visit, Penny mentions her father and reveals his name to be Bob.

Later on in the series, Penny’s father actually shows up in the show, but for some reason his name is now Wyatt, not Bob. Leaving Penny’s last name a mystery is one thing, but having her forget her own father’s name is a big mistake. 

19 Sheldon’s Germaphobia Is Abandoned

Penny and Sheldon Cooper in The Big Bang Theory

In season 4 episode 21, Amy, Bernadette, and Penny find out that Sheldon has kissed very few people because of his germaphobia. He explains that he hasn’t kissed anyone besides his mother, sister, his mee-maw, and a nun.

He explains that the nun passed out on a bus due to heat exhaustion, which forced him to perform mouth-to-mouth resuscitation. While some people would surely step in and perform CPR to save someone’s life, Sheldon doesn’t seem the type given his character’s extreme case of germaphobia. 

18 Did Sheldon Time Travel?

Jim Parsons as Sheldon Cooper in The Big Bang Theory

In the episode “The Dumpling Paradox”, Penny sleeps over on the couch at Sheldon’s place. This makes him miss the first part of Doctor Who, which he watches every Saturday morning. The night before, the friends played Halo, which always takes place on a Wednesday.

While the gang could have just played an extra night of Halo on Friday, it seems unlikely since Sheldon always has a strict schedule. Since Sheldon is incredibly smart, it isn’t too much of a stretch to imagine him time traveling, but this mistake just seems more like a plot hole with Sheldon's schedule. 

17 Sheldon’s Allergy To Cats

The Big Bang Theory Sheldon Cats

Leonard often has to avoid many foods and animals because of his allergies, but Sheldon is also very allergic to cats. His allergy is established early on in the series, but in the fourth season during the episode “The Zazzy Substitution”, Sheldon brings home not one, not two, but six furry, feline friends.

This not only goes against the Roommate Agreement that he himself created, but he also would have had a massive allergic reaction from being around so many cats. This is yet another example of the show going against continuity just to create a one time gag. 

16 The Joke About Howard’s Mom Is Disproven

Simon Helberg as Howard Wolowitz in The Big Bang Theory

Howard’s mom might not be a main character on the show, but she is mentioned quite often. For a good stretch of the series, there was a running joke that Mrs. Wolowitz was incredibly unattractive and overweight, so overweight, in fact, that she can’t walk. While the show makes this a recurring gag, they weren’t very careful about not showing Howard’s mom.

Mrs. Wolowitz has actually been seen a few times during the show and was even shown walking in the background during a scene where Raj comes over for dinner. Pictures of her can also be seen hanging on a wall, where she doesn’t appear to be overweight at all. 

15 The Roommate Agreements Are Often Broken

One of the many clauses in Sheldon’s Roommate Agreement explains that Sheldon must know a minimum of 12 hours in advance if Leonard wants to have a house guest over. That being said, this rule is often broken without Sheldon making it a huge problem, such as when Stephanie, Penny, and Leslie spend the night.

Sheldon himself has even broken the Roommate Agreement, since he brought home six cats, and cybernetically-enhanced helper monkeys and seeing-eye dogs are the only pets allowed in one of the clauses. 

14 Their Gas Station Is Actually Five Miles Away

The Big Bang Theory Gang on the Roof

It is stated several times in The Big Bang Theory that their apartment building is located at 2311 N. Los Robles Avenue, Pasadena, California. It is also mentioned more than once that there is a gas station right across the street from their building.

While this seems plausible at first, a simple Google Maps search reveals that the Colorado Boulevard Chevron is actually five miles away from their apartment building. This is also revealed in an aerial shot during the season 5 finale after Howard and Bernadette get married.

13 Sheldon’s Dancing Skills

Sheldon Dancing in The Big Bang Theory

For the first three seasons of The Big Bang Theory, Sheldon says that he doesn’t know how to dance and has no desire to anyway. That being said, in season 4 episode 21 “The Agreement Dissection”, the writers reveal that he actually does know a lot about dancing.

This is revealed when he is talking to Bernadette, Penny, and Amy, and he reveals that he was forced to take cotillion training as a boy. This not only goes against what was previously established in the show, but it also created a plot hole just for one silly joke. 

12 Sheldon Becomes Forgetful When It Works For The Story

Sheldon and Leonard in The Big Bang Theory

Sheldon Cooper is by far one of the most intelligent characters on The Big Bang Theory, but he also has an eidetic memory. This means that Sheldon can remember words and images after only reading or seeing them once. That being said, when the story calls for it, Sheldon becomes very forgetful.

In one episode, Sheldon rolls a dice to decide how he is going to react to everyday situations, but he has to repeatedly look at the list of rules in his notebook. If he really had that great of a memory, he wouldn’t have had to refer back to a notebook, especially since he created the list himself. 

11 Sheldon Survived The Helium Room

The Big Bang Theory Sheldon

The Big Bang Theory has had its fair share of scenarios that would never happen, but one of the most unrealistic moments of the show revolves around helium gas. In season 3, Barry Kripke fills a room full of helium while Sheldon is talking on a radio show.

While Sheldon sucking helium may have been a funny scene, it was actually very dangerous. Sheldon likely wouldn’t have survived this scenario in real life, since filling a room with helium could cause someone to suffer from oxygen deprivation. 

10 Was Leonard At Comic-Con Or In The Arctic?

Leonard's Thundercats Sketch from The Big Bang Theory

In season 2 of The Big Bang Theory, Leonard goes on an expedition to the Arctic with Sheldon, Raj, and Howard. It was considered a once in a lifetime opportunity, which took place in the summer of 2009. That being said, Leonard explains later on in season 5 that he actually went to Comic-Con in the summer of 2009.

He even dressed up as Lion-O from The Thundercats, and got a sketch of himself done by Jim Lee. While Leonard could have traveled back home to go to Comic-Con and then gone back to the Arctic, it seems incredibly unlikely and is probably just a plot hole. 

9 Sheldon Makes Up A Myth About Einstein

Sheldon Cooper isn’t afraid to say that he is one of the smartest people alive. He knows how smart he is, and isn’t always modest about the fact. He even once compared himself to Albert Einstein, but not in the way fans expected. When he begins working for Amy, she gets upset that Sheldon refuses to do tasks he finds degrading.

He then compares himself to Einstein, saying that Einstein failed math because he didn’t feel challenged enough. Not only is that a made up myth, but it doesn’t make any sense that Sheldon wouldn’t be aware that he just made a false statement. 

8 The Plot Line About Raj Being Scared Of Women Is Forgotten

In the very first season of The Big Bang Theory, it is revealed that Raj is terrified to talk to women. Raj eventually gets better as the series progressed, but for the longest time, he struggled to find love and talking to the opposite gender. That being said, that plotline was forgotten in the seventh episode of the show.

In the episode, Raj talks to Leonard right in front of Penny, and he has no reaction about talking in front of a girl. Raj becomes more comfortable around Penny as she becomes part of the gang, but he certainly wasn’t that comfortable with her in the seventh episode. 

7 Sheldon’s Knowledge

Sheldon Crazy

Sheldon Cooper is supposed to be incredibly smart, both with science and with pop culture references. That being said, Sheldon actually gets a lot of science facts and pop culture references wrong.

For instance, he once spelled the word “fusion” wrong on a whiteboard, and said that hitting a fork on a wine glass makes a sound in B flat when it is actually just B. He has also gotten pop culture references wrong by confusing Gremlins with Mogwais and by getting the details of Superman saving Lois Lane wrong. 

6 Sheldon Doesn’t Recognize His Father

The Big Bang Theory Lance Barber

While the show Young Sheldon didn’t premiere until 2017, one major actor from the show appeared in The Big Bang Theory. Actor Lance Barber appeared in season 5 of The Big Bang Theory in the episode “The Speckerman Recurrence” and was later cast as Sheldon’s dad in Young Sheldon.

This created a plot hole for season 5 of The Big Bang Theory since Sheldon doesn’t recognize his father, or even comment that he looks exactly like his dad. The showrunners of The Big Bang Theory had no way of knowing that the actor would later be used in Young Sheldon, but it creates a plot hole none the less. 

5 Howard Couldn’t Have Gone To Space

Howard in space in The Big Bang Theory

Another plot hole the writers of The Big Bang Theory create is in season 5 when they decide to send Howard into space. While this was a dream come true for Howard, it never would have happened in real life. Howard has a high risk of heart disease, seasickness, arrhythmia, and a nut allergy, making it nearly impossible for him to become an astronaut.

Astronauts also have to go through multiple tests to make sure can stay fit under the conditions of space and won't panic once they are in orbit, which makes Howard hardly seem qualified. 

4 Whose Out Of Whose League?

Penny and Leonard in The Big Bang Theory

Right off the bat, it was made clear that Penny was out of Leonard’s league. Despite this belief, Leonard is still able to become romantically involved with Penny and even ends up marrying her.

Their relationship has gone through its ups and downs, but later on in the series, viewers are made to think that Leonard actually settled for Penny since Penny is the one seen struggling to fix their relationship. If that is the case, there was a sudden shift in their relationship that was never developed or explained in the series and left fans scratching their heads. 

3 Penny’s Job

At the beginning of the series, it is revealed that Penny is a struggling actress who has to work at The Cheesecake Factory to make ends meet. The fact that Penny can afford an apartment in the same building as Leonard and Sheldon is a mystery in its self, but her career takes an unexpected turn in later seasons.

Bernadette is able to get Penny a job as a pharmaceutical representative, but Penny doesn’t have any background in medicine and was even a college dropout. 

2 Sheldon’s Parking Spot

Sheldon Cooper's Parking Spot in The Big Bang Theory

A recurring joke that The Big Bang Theory once had revolved around the guys having to constantly drive Sheldon around because he didn’t have a driver’s license. That being said, one episode in season 6 involved Sheldon and Howard fighting over Sheldon’s parking spot at their school.

If Sheldon doesn’t have a license let alone a car, it’s puzzling why this would be a big deal to Sheldon. Sheldon is later revealed to have gotten his license, but that doesn’t fix this mistake in season 6. 

1 Sheldon’s Financial Situation

The Big Bang Theory Sheldon

Sheldon Cooper may have a lot of valuable collectibles, but he used to be depicted as having money troubles. In the first season it’s revealed that he has money troubles, but later on in season 3, Leonard finds a ton of unopened and uncashed paychecks.

If Sheldon really did have financial issues, he would have cashed his paychecks and not lent money to Penny in the episode “The Financial Permeability”. Sheldon says he never cashed his checks because he doesn’t trust banks, but Sheldon also should have been smart enough to know that the paychecks are worthless if they aren’t cashed. 


Are there any other plot holes you know of in The Big Bang Theory? Sound off in the comments below!

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