Blossom

Q: Who was the titular character in 1990s sitcom "Blossom"?

A: Mayim Bialik

In season one of the Big Bang Theory, Raj suggests getting the girl who plays Blossom to join their Physics Bowl Team (as seen below). After her run on Blossom, Mayim Bialik went on to earn a doctorate in neuroscience. 

Then in the third season of The Big Bang Theory, Mayim Bialik joins the cast as Amy Farrah Fowler!