Check your car, Penny - it's not the check engine light that's blinking.
It'll be four years ago this May since the The Big Bang Theory left our screens for good, though thanks to its persistent existence on streaming services - and its predecessor spin-off Young Sheldon - it's not left our minds. If anything, more questions have arisen since its finale, some of which have been neatly tidied up in Young Sheldon.
Seriously, if you haven't watched it, do. It explains so much of TBBT lore surrounding Sheldon and his family that it almost acts as homework. You watch The Big Bang Theory for the question and attempt to find the answer in Young Sheldon.
The Big Bang Theory's maintained relevancy in pop culture has, however, allowed the more eagle-eyed amongst us to uncover hidden details within the show that, either due to complete incompetence or intentional drops of information designed to infuriate its audience, leave so much to unpack. From vehicular goofs to tributes to late cast members, repeat viewings are required to catch each of these Easter eggs.
The Big Bang Theory, dissimilar to its scientific-centric characters, isn't complex. Each character usually only has one overarching trait to make them memorable and for Raj, it's his increased loneliness and inability to form a stable sexual relationship.
In season ten's "The Allowance Evaporation", the concept makes Raj depressed as he's unable to find a suitable plus-one for Howard and Bernadette's wedding.
Alongside two unnamed brothers and one nameless sister, Adoot is the only other named family member mentioned. He's brought up by Raj in season five's "The Sibling Realignment", though is never seen in person.
In the season twelve episode "The D&D Vortex", Sheldon visits Wil Wheaton's house as a means of apologising to his enemy after projectile vomiting on William Shatner on Wheaton's Professor Proton show, with Shatner coincidentally being at Wil's house at the time as part of a celebrity Dungeons and Dragons group. Also in attendance are Kevin Smith, Joe Manganiello, Kareem Abdul-Jabbar, and, oddly, Stuart.
As detected by , Wil Wheaton's house number is 1701. A needless tidbit of information to the common eye, it's a major hidden detail to fans of Star Trek: The Next Generation.
You can believe one of two stories here, either the house used in the show actually is registered as 1701 or the crew decided to give a nod to Wheaton's past life. Either way, it's a scrupulous slither of information for Trekkies to relish in.
Throughout the series, it's extremely common to see anyone - from Howard, Raj, and the rest of the gang to various delivery drivers - freely enter Sheldon, Leonard, and Penny's apartment building.
As shown in season eleven's "The Gates Excitation", the front door requires a key to open. In this episode, Sheldon went inside and instead of holding the door for Leonard to follow, he didn't, causing it to shut and Leonard to have to use his key.
Though it's plausible that those living in the complex have the ability to buzz in visitors, as is trivial with such buildings, it's strange that this is never acknowledged and visitors just show up on the regular.
This isn't the only niggling issue with the apartment building either.
A great detail hidden in plain sight of the viewer, the apartments rented by Penny, and Leonard and Sheldon - and subsequently by Penny and Leonard, and Sheldon and Amy - each have a doorbell that is never used.
Their existence is entirely ignored; much like the elevator, the lack of the doorbells' use could be explained to the viewer amongst a regular discussion or, if needs must, in a flashback scene.
Perhaps they were rendered useless following the elevator's explosion? Either way, their nonexistence means Sheldon gets to carry on his three-knock procedure.
Heading back to "The D&D Vortex", upon learning of Wil Wheaton's celebrity Dungeons and Dragons group, Sheldon attempts to dissect who else may be playing by way of graph theory. Amongst the names is a litany of pop culture icons, including George Takei and Robert Downey, Jr. , however, is the name of Sean Astin.
Best known for playing Samwise Gamgee in The Lord of the Rings trilogy, Astin has closer ties to The Big Bang Theory than you may think, as he played Dr Greg Pemberton across three season twelve episodes; "The Confirmation Polarization", "The Laureate Accumulation", and "The Plagiarism Schism".
Perhaps it was an astute coincidence that the writers forgot Sean Astin had made his series debut by the time the episode premiered, but it seems too wise an inclusion for this to be an error.
In the season four episode "The Toast Derivation", Leonard and Howard decide to have dinner at Raj's apartment one night, owing to Priya - at the time Leonard's girlfriend - living with her brother.
Or, rather, "adness".
To him, eating elsewhere was as crazy as not using the letter M, which causes his sentence to become "This is adness. This is utter and complete adness". Notice the mistake? Sheldon forgot about the M in complete.
In retrospect, this was perhaps an intentional move from the writers and if not, they probably saw how much of a reaction it got from the studio audience and kept the quote-unquote mistake in the final televised edit.
This is a particularly exceptional from users of The Big Bang Theory's IMDb page.
Whenever the front lobby to the apartment complex is shown, there are sixteen mailboxes on display, indicating sixteen apartments in the complex. This is far from the correct number, however, as there are actually only eight apartments in the building, for a total of two apartments per floor. There are no apartments on the first floor - where the mailboxes are - and two on each of the floors ascended by the gang before they reach their own landing.
It's well documented that there are no hidden apartments on each floor either, as the purported 'missing' fourth wall has long been established as the outer wall, the one where Sheldon can open a window to create that illustrious cross-breeze he so desperately craves in the apartment.
There have been several references to the real-life Mayim Bialik's time playing Blossom Russo on the eponymous nineties show; perhaps the most memorable occurrence came in the very first season as Raj suggested "the girl who played TV's Blossom" as the fourth member of his, Leonard, and Howard's Physics Bowl group.
Another secret reference slid its way into the show's later seasons, though, as in season six's "The Holographic Excitation", Sheldon and Amy create a Venn diagram to decide on their Halloween couples costume for the party Stuart is hosting at the comic book store. Many typical Big Bang Theory references are made here, particularly on Sheldon's side of the board as he lists R2-D2 and C-3PO, Batman and Robin, and the Doctor and a Dalek as possible costumes.
On Amy's side, however, are some more traditional couples costume ideas. Cinderella and Prince Charming, Romeo and Juliet, Jack and Rose, and Blossom and Joey.
Here's a nifty detail that's actually more commonplace in television than you may think. When there's a scene depicting the gang travelling in a car, the headrests in the front two seats are typically altered to lower them more than they should be or, more regularly, removed altogether.
This provides viewers with a better vision of those sitting in the back. Take the below scene for example from The Big Bang Theory's season three episode "The Creepy Candy Coating Corollary". While in the car with Howard and Bernadette sitting directly behind them, neither Leonard nor Penny has a headrest to protect them, creating a clearer visual of Howard and Bernadette.
Eagle-eyed viewers have also spotted that, sometimes, there are no rear-view mirrors, either.
The gifting of jewellery is a routine move by The Big Bang Theory's male gang as a means of showing their affection to their respective partners. Leonard gave Penny a heart-shaped locket with his face on it before he left for an overseas expedition, whereas Sheldon gifted a tiara to Amy as a means of apologising for being less-than-enthused about Amy's paper being published on the cover of the Neuron magazine - but there's been no better gift given than the star necklace Howard gave to Bernadette.
Given to his soon-to-be wife in the season five finale "The Countdown Reflection", Howard promises to take the necklace to the International Space Station, thus giving Bernadette a gift that no one else could possibly give her; a star from outer space.
But what you probably didn't know is that Bernadette is seen numerous times throughout the subsequent seven seasons wearing the very necklace, replacing the cross necklace she wore prior. The move was a rare, genuine act of love from Howard, so it's little wonder as to why Bernadette opted to wear it every day.
Season three's "The Excelsior Acquisition" saw a classic Big Bang Theory moment as Sheldon was jailed for running a red light while taking an injured Penny to the hospital.
During the court scene, however, we see that the judge is Judge J. Kirby. An otherwise worthless fact it may be to the casual viewer, the name J. Kirby means only one man to diehard comic book readers: Jack Kirby.
The late war veteran was a legendary figure within the comic book world, creating such illustrious characters as the Incredible Hulk, Iron Man, and Thor, and producing work for both DC and Marvel alongside a host of other publications.
Acclaimed sitcoms would be nothing without their dedicated fandoms, but often this can come back to hurt them. The unravelling of plot holes is where social media's finest detectives lurk in the shadows and for The Big Bang Theory, this meant questioning Sheldon's purported cat allergy.
In season one's "The Fuzzy Boots Corollary", Leonard is left dejected upon seeing Penny kiss another man and being romantically rejected by Leslie Winkle, leading to him adopting a cat. This is when Sheldon's asthma and supposed allergic reaction to cats is made known, however, by the show's fourth season, he has made a miraculous recovery.
He himself adopts a cat - Dr Robert Oppenheimer - in "The Zazzy Substitution" after he and Amy break up, with his newfound love of felines quickly skyrocketing to the point his and Leonard's apartment is full of cats. Sheldon doesn't sneeze once during this entire process, and when Leonard brings Sheldon's mother in to talk some sense into him, she ignores his supposed asthma condition as well.
So, was it the case that Sheldon never had asthma and only told Leonard as a means of keeping the apartment animal-free, or was it a lack of attention from The Big Bang Theory's writers? You decide.
Here's a heartwarming detail about the guys' apartment. Following the sudden passing of Mrs Wolowitz in the season eight episode "The Comic Book Store Regeneration", a wallet-size picture of Carol Ann Sussi - the actress who voiced the overbearing Wolowitz mother who actually passed away - can be seen in each subsequent episode.
This, it seems, was a gesture from Johnny Galecki, who plays Leonard, and Steve Molaro, the Big Bang Theory's showrunner. Molaro to the Hollywood Reporter during a 2015 interview, explaining how the decision was made early on to have this as a tribute to Sussi:-
"After we had that impromptu memorial the morning she passed away, Johnny and I were hugging - like everybody was - and right then we found our prop person and asked to get a little picture of Carol Ann and we put it on the refrigerator [in Leonard and Sheldon's kitchen] so she's there in every episode now. It's so small you wouldn't even see it, but on the fridge is this tiny little wallet-size picture of Carol Ann that's been there since the day she passed away.
It's a brilliant tribute to a typically unseen member of the cast.
When they're not at Caltech, in their apartments, or at the Cheesecake Factory, then chances are the gang are hanging out at the comic book store. Frequented as often as their apartments, the store allows Leonard, Sheldon, Howard, Raj, and at times their partners the chance to browse the latest comic books, t-shirts, memorabilia, etc.
Take a closer look, though, and you'll notice that the store features roughly 99% DC Comics-related merchandise.
It's not an oversight from the prop department; it's a logical bit of product placement from Warner Bros, the overarching media family that encompasses The Big Bang Theory. DC is owned by Warner Bros, too, thus making it easier to include an abundance of DC products in the show.
Very rarely has the store featured products from other franchises, though it has happened, such as in season five's "The Russian Rocket Reaction", where Leonard and Sheldon purchase a LongClaw sword from Game of Thrones.
Throughout the Big Bang Theory, Penny's car constantly having its check engine light flickering became a semi-focal part of her character. Every scene in her car would typically see this brought up in conversation, particularly if she was travelling with Sheldon.
But Penny's car - her first one, anyway, which was a red 1980s Volkswagen Cabriolet MK1 convertible - wouldn't have a check engine light. Volkswagen vehicles from this era didn't come with a check engine light unless they had computerised engine controls, meaning that either it was another oversight from the writing department or Penny wasn't driving the car everyone thought she was.
Or, did Sheldon spot the wrong light?
Probably not.
