Comedy legend Bob Newhart is to guest star on the award-winning US comedy The Big Bang Theory.

The six-time Emmy-nominated star of The Bob Newhart Show and Newhart will play Professor Proton, the former host of Sheldon’s favourite childhood science show.

According to TV Line, Sheldon tracks his idol down online and discovers that he can be hired for parties and events - so Sheldon books him to come to his apartment.