Johnny Galecki

'The Big Bang Theory’ star - who played scientist Leonard Hofstadter - didn't impress his co-stars on the CBS sitcom with his nasty habit of sticking his used gum on a set wall.

Kunal Nayyar - who played Raj Koothrappali - said: "I'm not joking; there's a wall of 3,000 dried chewing gum from Johnny Galecki."