Over its incredible 12-year run, The Big Bang Theory finally called it quits back in 2019. After following a group of nerdy scientists, and their new neighbor and aspiring actress, Penny, the show became a massive hit. Given that the main characters were huge geeks themselves, the show, quite fittingly, was filled with loads of references and Easter eggs.
Whether hiding secret numbers with mathematical significance, or slipping in a few references to some of our favorite franchises like Marvel, Star Wars, and Indiana Jones, the show managed to hide some of them so well that most fans didn't even notice after their first viewing.
10 Sheldon's Favorite Number Has A Much Bigger Meaning Than Viewers Might Think
On various occasions throughout the show, Sheldon makes it pretty clear that his favorite number is 73. In fact, there are tons of occasions where Sheldon is seen wearing a t-shirt with the number 73 on it. But what's so significant about the number? For starters, 1973 was the year that Jim Parsons was actually born.
But, probably, more importantly, Sheldon loves the number thanks to its mathematical uniqueness. As he says "73 is the 21st prime number. Its mirror, 37, is the 12th and its mirror 21, is the product of multiplying 7 and 3... and in binary, 73 is a palindrome, 1001001, which backward is 1001001." So no wonder he loved the number so much!
9 Another Significant Number Is Seen On Many Occasions In The Show, This Time On Amy's Door
After the first few seasons, where the show became more and more popular, the writers felt it was time to add in two new main characters to the cast. One was microbiologist Bernadette, who eventually was married to Howard, the other was Amy Farrah Fowler, who was a neuroscientist.
Before her romance with Sheldon properly began and the two moved in together, Amy had an apartment of her own, which had a pretty significant apartment number, 314. While this may seem random, it is actually the first three digits of the famous mathematical constant "Pi,"or in numbers is 3.1415926535897... and so on.
8 Amy Was First Introduced In Season 3, But She Was Mentioned All The Way Back In Season 1
Amy was one of the best characters to be introduced apart from the main original five. She was smart, funny, and the perfect match for Sheldon. Her first appearance in the Season 3 finale was a turning point in the series, but some eager fans noticed that she was actually mentioned briefly all the way back in Season 1.
While Leonard was trying to find a replacement for Sheldon for their Physics Bowl team, Raj casually mentioned "You know who's apparently very smart, the girl who played TV's Blossom. She's got a Ph.D. in neuroscience or something." Yes, that very actress is Mayim Bialik, who went on to play Amy.
7 The Show Was Filled With Easter Eggs From The Galaxy, Far Far Away
Of course, given that their main circle of friends is filled with geeks, Star Wars references were bound to pop up on multiple occasions. From huge cameos like Carrie Fisher, Mark Hamill, and James Earl Jones, or the glaringly obvious, LEGO Death Star built by Sheldon from "The Isolation Permutation," the show had plenty of them.
But perhaps the subtlest, and somewhat coolest one of them all, was a simple username used by Sheldon. In "The Pants Alternative," after waking up from an evening of overcoming his fear of public speaking, Sheldon loads up a video of his drunken antics on YouTube, some fans noticed his username as 'ob1' in the top right corner, which of course is a reference to Obi-Wan Kenobi.
6 Another Massive Franchise Was Also Referenced A Lot, Indiana Jones
One of the most popular franchises over the past few decades was the Harrison Ford-led Indiana Jones saga. In fact, the show's reference was so sneaky, that viewers had to look at a whiteboard of equations to find it out. While usually, thanks to the help of UCLA professor David Saltzberg, the equations seen on the show were always correct and up-to-date with contemporary physics.
One whiteboard, however, in "The Raiders Minimization" swapped out real equations for the ones used in Raiders of the Lost Ark instead. This fun little nod to Indiana Jones was fitting for the episode, especially since Amy managed to spoil Indiana Jones for everyone in the entire world.
5 Marvel Comics Legend Jack Kirby Also Got An Awesome Little Mention
The Marvel Universe, whether that be the comics or the movies, was always mentioned repeatedly by the characters of The Big Bang Theory, and in one particular episode, the most famous man in Marvel made a guest star debut appearance, and that was Stan Lee. Lee is known as the creator of many incredibly iconic superheroes, but as great as he was, he wasn't alone.
In fact, his regular collaborator, Jack Kirby, was as influential as Lee in the creation of many characters, from the Fantastic Four to X-Men and the Hulk. Sadly, he passed away before The Big Bang Theory, but he was still given a mention in that same episode, where the judge sentencing Sheldon to jail was named after him.
4 Who Would Have Thought That Both Leonard & Sheldon's Names Were Inspired By Physicists?
Leonard Hofstadter and Sheldon Cooper are now massive names in the TV world, which might have been a surprise before the show since they are both incredibly nerdy scientists and comic book buffs. Their names aren't the most common of names either, but the inspiration for them both came from world-renowned scientists.
Robert Hofstadter was a Nobel Prize in Physics winner in 1961, for his ground-breaking work in electrons, and Leon Cooper also won a Nobel Prize thanks to his discovery of 'the Cooper pair.' What's more, their first names both originate from American film and television director, writer, and actor Sheldon Leonard.
3 Where Did Sheldon's Iconic "Bazinga" Catchphrase Actually Come From?
"Bazinga" was used on multiple hilarious occasions on The Big Bang Theory by Sheldon Cooper as a way to tell people that what he just said was actually a joke. The term became a running gag in the show and many fans loved it, but the origins of the word would make fans laugh even more.
The term was actually coined by Stephen Engel, a writer on the show, who loved playing pranks on the cast and crew. One such prank involved him hollowing a grapefruit, putting it back together, and giving it to writer Bill Prady. When it fell apart on Prady, Engel yelled "Bazinga," and the phrase was born.
2 Did You Know That "Soft Kitty, Warm Kitty" Is Actually A Song From The '30s?
Another repeated gag from the show, and perhaps one of the funniest of them all, is the song "Soft Kitty, Warm Kitty." It was the song Sheldon's mother used to sing when Sheldon was feeling sick, and later Sheldon continued to use whenever he was ill, even as an adult, and even sang it to others when they felt under the weather.
But, in what might come as a bit of a shock, the song actually originated in the '30s and was written by Edith Newlin. The song was featured on another show in Australia, where Prady's daughter heard it and inspired the writers to add it to the series, and we are so glad that they did.
1 Penny's Fridge Is Actually Full Of Easter Eggs
Penny's fridge was always known to be full of photos from her life, but upon further inspection, all the photos are actually of Kaley Cuoco with the cast and crew over the years of filming. Some include her with Mayim Bialik and Melissa Rauch, who played Amy and Bernadette respectively.
Another of the photos even feature Carol Ann Susi, who voiced Howard's mom, and sadly passed away during Season 8. The fridge is a nice little memoir for the cast and crew, and we are glad that some fans noticed the lovely touch.