Currently in the midst of airing its last ever season at the time of this writing, when all is said and done The Big Bang Theory will have lasted an impressive twelve seasons. Over that time, audiences have been introduced to a long list of characters that will be remembered for many years to come, which is why the show’s legacy has already been cemented.

Clearly, The Big Bang Theory is destined to live on in reruns for many years to come, which will give fans of the show many more opportunities to examine its tiniest details. Unfortunately, upon further examination one thing will become abundantly clear: there are some pretty notable mistakes at the heart of the series. While some of these errors are completely forgivable, there are others that are so inconsistent with the show’s characters that they are pretty hard to take. Despite that, many viewers has failed to ever take note of them.

In order for something to appear on this list, it first and foremost needs to relate to The Big Bang Theory in one way or another. On top of that, it has to be something that is inconsistent with a different story point the show has revealed in the past. That said, these mistakes are more significant simple continuity errors, so you won’t find any entries about things like props changing position from one shot to another.

Here are 20 Mistakes Fans Completely Missed In The Big Bang Theory.

Howard Could Never Qualify to be an Astronaut

The Big Bang Theory Howard

At the end of the fifth season the show sent Howard into space. A storyline that continued over several episodes, during the first part of the sixth season audiences got a window into his exploits in space. However, it made no sense whatsoever that he managed to become an astronaut at all. Even his last-minute inclusion on the team does not explain that away.

The man’s various health issues would disqualify him from taking on the role.

After all, fans know that he suffers from a high risk of heart disease, seasickness, arrhythmia, and he is allergic to nuts, which are a staple of space travel.

The Gang Does Not Know How to Use Salt and Pepper Grinders

The Big Bang Theory Sheldon

This is the kind of mistake that you could see a thousand times and never take note of it, but once you do, it is all you can see. As is the case with most sitcoms, this show uses the same sets over and over again. For instance, many scenes take place in the cafeteria at Raj, Howard, Leonard, and Sheldon’s work.

It's the location where the guys often discuss their issues of the week over lunch. Since they rarely eat anything, the actors often do things like sprinkling salt or pepper on their food. Unfortunately, if you look closely the tables have salt and pepper grinders, so every time they act like they are salt and pepper shakers it is truly ridiculous.

Leonard’s Inconsistent Snoring

Leonard Hoftstadter flirts with Penny in The Big Bang Theory

Let’s face it, if you have ever found yourself sleeping in the same room as someone that snores heavily it can be very annoying until you get used to it-- if that ever happens. Yet, in the world of The Big Bang Theory people are inconsistent about whether or not Leonard snores.

It was first brought up in a third-season episode, when Penny declared that Leonard does not snore.

The issue is then revisited five seasons later, in the sixth episode from season eight. Sheldon even lists Leonard’s lack of snoring as a positive aspect of being his roommate. However, only three episodes later, in the ninth episode from that same season, Leonard suddenly has a snoring problem due to a deviated septum. This is an issue that would be present from his birth.

Sheldon’s Handling of his Paycheques

Sheldon Cooper looking confused in The Big Bang Theory

One of the most interesting aspects of Sheldon Cooper’s personality is that he values his various collections but he barely seems to care about his finances. In fact, at one point, Howard goes into Sheldon’s desk and finds a pile of his paycheques that have never been opened, let alone cashed. Utterly flabbergasted, Howard asks Sheldon why he has so many piled up cheques. Completely nonchalant in response, Sheldon explains that he has so many cheques in part because he does not trust banks.

Sheldon is far too smart to not realize that cheques are only valuable because of the value banks assign them. His explanation is a reason to cash them instantly. On top of that, after a certain period of time, cheques are voided, so he would have to be totally ignorant to think his actions make any sense.

Sheldon’s Failing Memory

The Big Bang Theory Sheldon

Inarguably the most popular character from The Big Bang Theory, Sheldon is so beloved that many of the show’s most loyal viewers are overjoyed when episodes largely focus on him. More than that, when a storyline pops up that pushes him out of his comfort zone it can be a real delight for fans of the show. In a perfect example of that, Sheldon decided to let dice rolls decide how he reacted to any given situation for one episode.  There was one major problem with this, however.

Throughout the episode he consults a notepad,  where he wrote down the actions he assigned to each dice roll outcome.

That may be what most of us would do in that situation, but he has an eidetic memory, which means he should instantly know what he wrote without looking it up.

Leonard’s Inconsistent Relationship with Joyce Kim

Penny hugging Leonard in The Big Bang Theory.

The first couple from The Big Bang Theory to tie the knot, Penny and Leonard have been together long enough that it easy to forget about many of their exes at this point. Far less lucky at love than Penny, Leonard entered into some utterly doomed relationships prior to getting together with his eventual wife.

In fact, it was even revealed that he briefly got involved with a woman named Joyce Kim who turned out to be a North Korean spy. While that is no secret, how long they were together for is very unclear. At one point, it was explicitly stated they were together for 27 days, however, a later episode showed a flashback of Sheldon scaring Joyce off after only 12 hours.

Sheldon's Randomly Folded and Crumpled Money

The Big Bang Theory Sheldon

The second entry looking at Sheldon’s unique relationship with money, this time around we are looking at the way he has been shown handling actual cash. Unsure what to get Amy as a present in a sixth season episode, he has a brainstorm and asks his assistant to go out and get his lady perfect presents.

Sheldon knows enough to hand her the money needed for her shopping spree and gathers money from his pocket and desk.

Oddly enough, however, all of the cash he gives her is either crumpled up or randomly folded. No matter how disinterested in money he may be, Sheldon is far too hyper-organized to ever keep anything in his life in such a state of disarray.

Sheldon Survived in a Room that Was Pumped Full of Helium

The Big Bang Theory Sheldon

If someone tried to put together a list of every fictional character that spoke with a high helium-induced voice it would be insanely long. Though it's pretty amusing in the right circumstance, people should keep in mind that breathing helium actually is a lot more dangerous than popular media would have you believe.

Playing into that misperception, The Big Bang Theory featured a storyline in which Barry Kripke filled a room that Sheldon was in with so much helium that it altered his voice. Unfortunately, if a room was filled up with that much of the gas, it would be impossible for a human being to survive in for long due to oxygen deprivation.

Penny's gaming laptop isn't even on

One of the core concepts featured in the first several seasons of The Big Bang Theory revolved around the guys getting used to hanging out with an outsider like Penny. Though she's an extremely sweet woman, her background as a hard-partying popular girl is one that her new friends did not understand.

Penny struggled to understand many of the things the guys love so much, including their passion for gaming.

Then came an episode in which Penny suddenly becomes addicted to a game that Sheldon shows her. At one point she goes to Sheldon to get help with the game but if you pay attention when she walks away, her laptop clearly wasn’t even on.

Other People Sat in Sheldon's "spot" and he Didn’t Care

The Big Bang Theory Couch

Because all of the main characters are well aware that Sheldon has a spot on the couch, none of them need to be reminded of that fact anymore. However, if you go back to the early seasons, it came up somewhat regularly, often with amusing results. Sadly, if you pay attention during some of the episodes from the first season, it seems apparent that his feelings about his spot were either forgotten or not planned from the start.

There are a pair of scenes where both Leonard and Raj are seen sitting in his spot to zero reaction.

In fact, in one instance, Sheldon even sat somewhere else on the couch.

Inconsistent Reasons the Elevator Doesn’t Work

The Big Bang Theory Failed Experiment

Set designers fill up the background of scenes and those details can make all the difference in the world. An interesting example of that, the permanently elevator from The Big Bang Theory has become a staple of the show. Despite that, the explanations been all over the place when it comes to what took the elevator out.

For example, during the first season, they say it stopped working two years ago, but in season three, the timeline was pushed back by three years. On top of that, an experiment that went awry was witnessed by all of the guys and was shown causing the damage to the elevator. Yet somehow, several seasons later Howard spent hours trying to figure out what happened to the elevator, despite witnessing the incident.

Leonard Went to Comic-Con While He Was in the Arctic

The Big Bang Theory Lion-O

For most people, spending months of your life doing research in the Arctic is going to be a once in a lifetime experience. In Leonard’s case, his time in the Arctic should be especially noteworthy since he was welcomed back to a passionate embrace from Penny, the woman of his dreams. Still, a couple of seasons after all of that took place, Leonard claimed that he attended Comic-Con when he actually was abroad.

Maybe this could be explained away as a mistake in his memory.

Unfortunately, that was undermined by his specific memory of getting a sketch of himself as Lion-O from The Thundercats that year, and he even showed off the drawing to prove it.

Sheldon Doesn’t Know the Difference between Gremlins and a Mogwai

Gremlins Sad Mogwai

Kids from the '80stend to hold many of those films extremely close to their hearts. Included among that group is the Christmas horror film Gremlins. It's exactly the kind of movie that you would expect the guys from The Big Bang Theory to be experts on. In a third-season episode of the show Sheldon even went on a rant about it.

Revealing his confusion that anyone would fail to follow the rules set up in the film, he talks about not being able to feed Gremlins after midnight. Of course, anyone that remembers the movie well would know that rules apply to Mogwais, not Gremlins. Sheldon would never make that mistake.

Amy Isn’t Given the Title She Has Earned

The Big Bang Theory Raj

Without a doubt the character that has changed the most, Amy Farrah Fowler underwent a gigantic growth in her personality over time. However, her extreme intelligence and pride in that fact has remained a constant right from the start. On the other hand, the original plans for her character apparently did not involve one of her greatest scholastic achievements: the doctorate she earned. This is obvious because she took part in a science panel with the guys and her name tent did not have the title "Dr." on it.

Amy would not have taken an oversight like that lying down.

She was the only person on the stage to not have Dr. in front of their name- aside from Howard, who is known to not have a doctorate.

Getting the Details of Superman the Movie Wrong

Helicopter Rescue from Superman the Movie

This time around we’re looking at a pair of mistakes that relate to a beloved superhero movie. Known to be a devotee to superheroes, Sheldon collects pretty much anything related to that world, yet he got key elements from Superman: The Movie wrong. Speaking about the first time that Supes saves Lois Lane on film, Sheldon was very wrong even though many casual films could accurately describe the moment since it has gone down in cinematic history.

In an egregious moment, Sheldon claims Superman swooped down to grab Lois even though he flew up to her.

On top of that, he also says Lois was two feet from the ground when she was saved but she was still several stories in the air.

Sheldon Buys Into a Myth About Albert Einstein

Geoffrey Rush Albert Einstein Genius

There are only a select few minds from history that Sheldon sees as being in the same caliber as him. As such, when Sheldon positively compares his thirst for mental challenges to Albert Einstein, that is not a throwaway line for a character like him.

He was working for Amy in her lab at the time.

When she became frustrated that he would not do menial tasks, he claimed that Einstein failed math due to not feeling challenged.

This is something he should have never said, as it is a complete fallacy that Einstein failed math. Sheldon bringing up that completely false myth goes against everything fans know about him.

Sheldon Does Not Know What Color Luke Skywalker’s Lightsaber Is

The Big Bang Theory Sheldon Leonard

In yet another example of Sheldon being wrong about major things from pop culture, this time he failed to be accurate one of the biggest sci-fi franchises of all-time, Star Wars. Worse yet, it wasn’t even some arcane fact that he was off about. Instead, in a second season episode, he spoke about Luke Skywalker and his lightsaber, and was off on the details.

Trying to describe what color he wanted his car to be in a simulation at the time, he tells Howard to make it pale blue like Luke’s lightsaber. However, the biggest fans of the series, as Sheldon is, should know that Luke’s lightsaber was green and he only used a blue one while he wielded his father’s weapon.

Sheldon Adopting Cats Despite Being Allergic to Them

The Big Bang Theory Sheldon Cats

Many over the top geeks in our pop culture seem to be allergic to just about everything. It really is pretty weird this is a major part of so many nerdy characters and it even pops up in The Big Bang Theory. That said, in a somewhat unexpected twist, when it comes to this show, it is Leonard that has to steer clear of many items due to his allergies. Still, during the show’s early seasons, it is revealed that Sheldon will have a reaction if he interacts with cats.

Then, during the fourth season episode, "The Zazzy Substitution", Sheldon adopts six cats, which would bother most people that don’t have even a hint of an allergy problem.

Raj Suddenly Talked in Front of Penny

The Big Bang Theory Cast

It really is about time that Raj gets to attain some happiness in the love department. After all, at first, it was amusing that he was such a failure with the opposite gender, but over time it has just become sad, especially as he has become more defined by his love for the concept of romance.

Of course, that isn’t to say he hasn’t improved with women at all, as evidenced by the fact that when the show began he couldn’t speak to women at all. Well, that was supposed to be his defining character trait, but in the seventh episode of the show, he speaks to Leonard in front of Penny while completely sober.

Sheldon Doesn’t Recognize Someone Who Looks Exactly Like His Father

The Big Bang Theory Lance Barber

This mistake only exists because The Big Bang Theory received a spin-off. Young Sheldon gave fans the opportunity to see the most popular character from the franchise as a child. Even more entertainingly, viewers have also gotten to know Sheldon’s entire family, including George, his father who passed away unfortunately early in life.

Though he's pretty great in the role, the casting of Lance Barber as Sheldon’s dad caused a serious problem because he’d played a supporting character in the original series.

As a result, scenes from The Big Bang Theory episode title "The Speckerman Recurrence" feature Sheldon interacting with someone who looks exactly like his dad, without showing any sign of recognition.

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What other mistakes did we miss in The Big Bang Theory? Let us know in the comments!