This post will only be amusing if you have watched "Singing in the Rain" :)
Donald O'Connor (Cosmo) got extreme carpet during the song "Make em' Laugh" then had to re do the whole song when the original footage was ruined.
The man who played Don Lockwood and the girl who played Lina Lamont both of their names were Jean. Except spelled different ways. :)
Well that's about it. Do you like facts about movies? Or do you prefer words?