There were a lot of stories about the actors playing the Munchkins being rowdy on set and at the premiere (including the incredibly weird and dubious one that they would run off between takes and handlers were there to catch them with nets) but they seem to have little basis in fact or are highly exaggerated. Several of the Munchkin actors who survived until fairly recently used back against these stories. While the actors were excited to be part of the film, I don’t think they were particularly rowdy :)