Brando putting the cotton in his cheeks was widely known, but I've learned since I've been here mostly, that he was quite a prankster as well. As mentioned in the link, adding weights to his hospital bed, so it would make it heavier to lift.
And yet another injury when Caan, during the scene in which it beats Carlo, actually breaking two of Russo's ribs and elbow! Ouch!!! I guess Carlo really did get the sh*t beaten out of him.
Damn, it would have been so cool just to scene any one of the GF scenes being filmed.
TIS