Margo Harshman – Then
Margo Harshman appears in season 6 of the show playing the role of Alex Jensen, a graduate assistant working with Sheldon. She is hired to review his work to find any potential for Nobel Prize winning research. She becomes interested in Leonard, who is still dating Penny, which makes him feel quite good about himself but causes Penny to feel jealous. Sheldon gets upset and attempts to give her a talking to, which of course ends up going hilariously wrong.
Margo Harshman – Now
Following her role on Big Bang Theory, Harshman has appeared in TV shows like Betas, Bones, CSI: Crime Scene Investigation, NCIS, and most recently How I Met Your Father. She has also previously starred in shows like Everwood, Grey’s Anatomy, Journeyman, 90210, Boston Legal, Modern Family, and House.