Pirates of the Caribbean (Dead Man's Chest) - Disappearing Fish and Guts
Fast forward to the part where Will Turner is on the ship and he encounters Davy Jones's Crew (about an hour into the movie). He begins to fight the crew and he slays one of the pirates causing fish and guts to splatter across the deck next to him. Then 5 seconds later he gets knocked unconscious and he falls down on that same spot and the fish and guts have suddenly disappeared! This slipup is very easy to notice.