Star Wars

This may be one of the best slip-ups of all time. One of the Clone Troopers in Star Wars accidentally smashes his helmet on the rising door while they're patroling the Death Star. They probably did a bunch of takes where this actor didn't hit his head, but somehow, this one made the cut. It's honestly one of the funniest things to come out of the entire Star Wars franchise! It's probably hard to see with that big helmet on. 

Clueless

Even though Cher's stressful fail of a driving test, viewers noticed something a little weird about her Jeep. During her test, she veers into some parked cars and ends up tearing off her Jeep's side mirror. Her instructor, who is naturally horrified, tells her to pull onto a side street and stop the car. In the next frame, the mirror of the Jeep is magically back on the side of the car. Seems like continuity isn't a thing in this scene!