George Clooney and David O. Russell
George Clooney and David O. Russell worked together on the 1999 film Three Kings. Clooney took the main role while Russell directed. The two bashed heads constantly. Apparently, Clooney accused Russell of mistreating the production crew. This accusation turned into a physical fight that had to be broken up.
Leonardo DiCaprio and Claire Danes
Claire Danes and Leonardo DiCaprio made history with their roles in Romeo + Juliet. Both actors were very young while filming, so naturally, they butted heads. One time, he tried to play a prank on Danes, who did not find it funny. He felt that she was too uptight and thus began their uneasy relationship. Things changed for the better when they grew up, though!