When Frank is fishing the pen out of the fish tank and the fish gets attached to his nose, there is visible blood. When the camera cuts back to Frank, the blood is gone.
There is a trailer to this movie with an additional gag. After Ludwig has demonstrated his image of an ideal assassin to Papshmir, he sits down with the revolver used in the demonstration which had turned out to be empty. In the trailer shot (in a closeup of Montalban) the gun unexpectantly goes off.