All rise! Oh, wait, he isn’t that kind of president. Dr. Siebert is a physicist and the president of Caltech. He cares about funds and funding, and… that’s about it.
We meet him in season 3 for the first time, and his performances pepper the show for the rest of the show. In the 12th and final season, however, we get a much bigger dose of him, mainly thanks to the fact that Sheldon’s research is making progress and he’s in line for Nobel Prize.
Judd Hirsch as Alfred Hofstadter — Now
Judd Hirsch's impressive acting career stretches all the way back to the early 1970s! He started with a couple of tiny, uncredited roles and steadily climbed the ranks until getting his most memorable role as Alex Reiger in the TV show "Taxi," which ran for more than 100 episodes.
TBBT was a drop in the bucket of acting credits this actor has under his belt. After the show ended, he never went off screen and kept appearing regularly n a multitude of TV productions, and has even lent his voice to the Netflix hit adult cartoon "Big Mouth."
Regina King as Janine Davis — Then
In a show where most characters are awkward and socially inept, it's nice to occasionally be reminded of a normal person's perspective. Janine Davis is another Caltech employee, but she isn't a scientist. She works at the university's HR department, which makes her one of the very few sane voices on the show.
Whenever one of the main gang's men unknowingly does something inappropriate, you can trust Janine to lay down the law and explain some basic human etiquette. We very much appreciate her service.
Regina King as Janine Davis — Now
With a name so regal, you can't help but bow down to Regina King. Her acting career started with a bang when she landed the role of Brenda Jenkin in "227" — a role she stuck with for 5 years and 110 episodes. Not bad for a first gig!
Since then, this talented actress has been a series regular in more shows than we can count. ("24," "Southland," and "American Crime," just to name a few.) After TBBT was over, King went on to star a Sister Night (aka Angela Abar) in the hit superhero ministries, "Watchmen."
Joshua Malina as President Siebert — Now
Molina has been acting since the early 90s, mostly in minor roles, until he got his first big part as Jeremy Goodwin in "Sports Night." He did that for two years and went on to other projects, such as a series regular in "The West Wing" and "Scandal."
After TBBT, Malina was only cast in small TV roles, but we have no doubt we will see him doing something pretty big pretty soon.