The Big Bang Theory guest stars

A casting call has been put out by The Big Bang Theory for a "[DIMITRI] 
55-70. This man was a physicist in the former Soviet Union and is now a janitor in the lab where Sheldon works...GUEST STAR / ACTOR MUST BE ABLE TO DO A RUSSIAN ACCENT".

Credit: SpoilerTV.

We've been hearing that Laurie Metcalf, Jackie from Roseanne, would guest star on the show as Sheldon's mother for a while now but it was never official - well, now it is.

During last nights "Live from the Web Carpet", we heard Laurie Metcalf will indeed be on the show as Sheldon's mother.

Sara Gilbert (Darlene - "Roseanne") will reunite with former  "Roseanne" co-star Johnny Galecki (David - "Roseanne") on upcoming episodes of "The Big Bang Theory".

Galecki, whose character was married to Gilbert's character on "Roseanne", plays Leonard a geek who is uncomfortable with the opposite sex on CBS' "The Big Bang Theory".

Gilbert will play a potential love interest for Galecki's character, Leonard, in an untold number of episodes.