Sheldon has been a fan favorite since the start of the show. He is a Caltech theoretical physicist and was once roommates with Leonard, his best friend. He easily annoys those around him, has a very serious demeanor, and is anal about his routine.
He rocks his geekiness and his arrogance, believing himself to be perfect. He started dating neurobiologist Amy in season 5, and they become engaged in season 10.
John Galecki as Leonard Hofstadter – Then
We met Leonard during season 1 when he worked as an experimental physicist and Sheldon Cooper’s roommate and best friend. He loves Sheldon but often gets annoyed by his eccentricity.
Leonard is super smart, like the rest of his friends, and has a Ph.D. from Princeton, which he finished when he was the ripe age of 24. He fell in love with Penny, who has dreams of being an actress, and the two eventually tied the knot in the ninth season.
John Galecki as Leonard Hofstadter – Now
TBBT wasn’t John’s first acting gig, but it did make his name a well-known one. He now has several awards in his arsenal, including an Emmy for Outstanding Lead Actor in a Comedy Series.
John has since starred in other movies and television shows, but none have brought him success, like his role in this show. John’s role as Leonard made him a salary of $350,000 per episode until the 8th season, following a whopping increase to $900,000 per episode.
Jim Parsons as Sheldon Cooper – Now
Jim is another star of the show who found himself blossoming in his role as the beloved Sheldon. He has taken home a Golden Globe and an Emmy for his work.
You may have recognized his voice in the animated movie "Home," where he plays an eccentric and freethinking alien named Oh. Jim made $900,000 per episode (along with John and Kaley), making him one of the highest-paid actors in comedy television.
Sara Gilbert as Leslie Winkle – Then
Leslie works at Caltech with Leonard as a physicist. Leslie is a female carbon copy of Leonard, even dressing similarly in hoodie sweatshirts and black-framed glasses. In season 1, Leonard asked her out instead of Penny because he felt like Penny was too good of a catch for him.
Sheldon disapproves of their relationship, causing ongoing tension between the two. Ultimately, Leslie and Howard form a casual, no-strings-attached relationship, with Howard having emotional feelings towards her.