Back to the Future Part III - Verne points at his crank
Basically one of the kids/dwarf on the train using his hand signals something like "come here" and than point to his crotch.WTF??!!!
Anybody remember the ghost looking through the window in 'Three Men and a Baby', it was actually just a mannequin behind the door.

According to the YouTube uploader: “My friend noticed this back when the DVD set was released. I made this video back then and just found it so here you go.