Star Wars When the stormtroopers break into the control room, watch very carefully and you will be able to see a storm trooper nearly render himself unconscious by smacking his head off a door frame. This is now so notorious that on the new DVD there's an audible "bump" when he hits it.
Charlie's Angels When the Angels are fighting the "Creepy Thin Man," right before Drew Barrymore lifts up Lucy Liu to spin her around and kick the thin man, to get Lucy's attention, Drew hollers out "Lucy!" even though Lucy Liu's character's name is "Alex."
Harry Potter and the Philosopher's Stone When Harry, Ron and Hermione rush to Hagrid after the end of the year exams, and Harry is saying something that ends with, "Why didn't I see it before?", Hermione is mouthing his lines.
