The Big Bang Theory was a sitcom that quickly amassed a large following and fanbase, and ran from 2007 to 2019 with a whopping 12 seasons. Young Sheldon is a sitcom that began in 2017 and has six seasons so far, with one more season confirmed for the future as of now. Young Sheldon is a prequel series that follows one of the main Big Bang Theory cast members, fan-favorite character Sheldon Cooper, as a young child through his adolescent years. Since it is a prequel, there are a fair share of Easter eggs related to The Big Bang Theory that show up in Young Sheldon, and here are some you may have missed.

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Professor Proton

     Warner Bros.

In The Big Bang Theory, the character Professor Proton (aka Arthur Jeffries) is like our world’s Bill Nye, the Science Guy (played by the great Bob Newhart). He held a children’s show where he explained scientific concepts, and all the scientists of the gang grew up watching him. When they got to meet him in person, they are all star-struck.

In Young Sheldon season four, we see a signed autograph on a poster of Arthur Jeffries. Unfortunately, Missy rips it up during an argument, and Sheldon is crushed. Little does he know that Professor Proton will come over to his apartment later in The Big Bang Theory.

Sheldon’s Catchphrase: “Bazinga”

Early in The Big Bang Theory, it’s explained to the audience that if Sheldon is making a joke, he will end it with “Bazinga” to make sure people know he’s joking. This is used through all 12 seasons of the show.

In Young Sheldon season two, Sheldon visits a novelty shop and learns about a line of prank products. So naturally, the punchline of every joke is “Bazinga.” And so the catchphrase was born.

Sheldon and Trains

Throughout The Big Bang Theory, Sheldon has always had a love of trains. He’s mentioned the train store plenty of times and facts about trains in just as many instances. So it’s no understatement to say that he’s a fan of train collecting and train riding communities.

In Young Sheldon’s first episode, it makes sense to show this interest in trains from the beginning. Even the voiceover of adult Sheldon states, “I’ve always loved trains. In fact, if my career in theoretical physics hadn’t worked out, my backup plan was to become a professional ticket taker. Or a hobo.” This moment in the pilot instantly reminds the audience of the Sheldon Cooper they are used to in The Big Bang Theory.

Sheldon’s Sick Song

     CBS

There are a few moments throughout The Big Bang Theory where Sheldon gets sick, and the rest of the gang must make him feel better by treating him like his mother would. This includes singing him a lullaby called “Soft Kitty.”

In Young Sheldon, we see the same song sung by Sheldon’s Mother when Sheldon is not feeling well, showing the origins of “Soft Kitty.”

The CalTech Cafeteria Table

In The Big Bang Theory, the gang settles down for lunch at one table more than the rest. The fans have deemed it their spot, even if it’s not brought up in the show.

In season three of Young Sheldon, Sheldon makes his first trip to CalTech, a place where we all know he will be working one day. While viewing the cafeteria, he glances at the table that the gang will one day occupy.

“His Mother Had Him Tested.”

A running joke throughout The Big Bang Theory is that whenever anyone infers Sheldon is crazy, he very seriously tells them, “I’m not; my mother had me tested.” This is proven true when his mother says the same thing later in the series when she visits Sheldon.

In Young Sheldon, the same joke continues. The testing is said to have happened before both shows began, so the joke runs through Young Sheldon just as much as in The Big Bang Theory.

“Moonpie”

In The Big Bang Theory, Penny discovers letters from Sheldon’s Meemaw. In those letters, we learn that Sheldon’s grandmother called him Moonpie as a term of endearment.

In Young Sheldon, we see Meemaw as a naturally younger character than we are used to in The Big Bang Theory, and she constantly uses the nickname Moonpie when talking to him.

Relationship Agreements

     Warner Bros. Television

In The Big Bang Theory, Sheldon has a roommate agreement that Lenard must follow to live there, and likewise, one with his girlfriend, Amy, about the terms of their relationship. It’s a plot point that has caused trouble for all parties involved throughout the show.

Our first glimpse into such agreements made by Sheldon is when Meemaw and Sheldon’s mentor, Dr. John Sturgis, start to see each other romantically. So naturally, Sheldon makes an agreement for them to sign, stating what they can and can’t do. But of course, in Sheldon’s fashion, it makes his life more manageable, and everyone else’s harder.