Fans are happy th showrunners brought the characters back to Young Sheldon.

When The Big Bang Theory first aired in 2007, its target audience was roughly the same age as the main characters. As fans of the show matured along with the Pasadena gang, the writers expected them to watch the prequel, Young Sheldon — and that's what we all did!

So to keep fans engaged and pay homage to the original story, the showrunners re-introduced some TBBT characters in Young Sheldon, and we feel really thankful for that.

Professor Proton

Dr. Arthur Jeffries, better known as Professor Proton, was a host on a children's TV show, where he demonstrated scientific principles using everyday objects.

Sheldon and Leonard grew up watching the Professor Proton show, and it was thanks to him that they decided to become scientists.

The character first appeared on TBBT, but Young Sheldon continued the tradition to the delight of many fans: Professor Proton can also be seen in the prequel as the host of the show that Sheldon watches.

Tam Nguyen

Tam Nguyen was Sheldon's childhood best friend and classmate whose family fled Vietnam for the US. He introduced Sheldon to comic books and role-playing games.

The character first appeared in Young Sheldon and later in the original series, as the friends reunited after not speaking for 20 years.

George Jr. and Missy Cooper

Sheldon's elder brother and twin sister were played by Jerry O'Connell and Courtney Henggeler in the main show, and by Montana Jordan and Raegan Revord in the spin-off. The prequel explores these characters' lives and personalities much deeper, also showing how the siblings influenced Sheldon.

Mary Cooper

In TBBT and its prequel, Sheldon's mother is portrayed by two different actresses — Laurie Metcalf in the original show, and Zoe Perry in the spin-off. However, fans have noticed that the actresses look very much alike and also share similar mannerisms. Well, the reason for that is actually quite simple: Metcalf and Perry are mother and daughter, which makes them the perfect duo for the role.

Meemaw

Sheldon's grandmother Meemaw, portrayed by Annie Potts in Young Sheldon, is a fan-favorite character and an absolute antithesis of her religious daughter Mary.

Meemaw loves to drink, ride motorcycles, and gamble just so she doesn't get bored. Interestingly, she comes across as a completely different character in the original show, where actress June Squibb played the role.

The Gang

In addition to Sheldon himself, other members of the Pasadena gang appear briefly at the end of Season 2. We get to see Leonard, Raj, Penny, Howard, Amy, and Bernadette as young kids, and they're all yet to become friends in TBBT.