Marty: No wait, Doc, the bruise, the bruise on your head, i know how that happened, you told me the whole story. you were standing on your toilet and you  were hanging a click, and you fell. and you hit your head on the sink, and that´s when you came up with the idea for the flux capacitor, which makes time travel possible.

Marty: Something wrong with the starter, so i hid it.

Doc: After i fell off my toilet, i drew this

Marty Flux capacitor.

Doc: It works, ha ha ha ha, it works. I finally invent something that works.

Marty: Bet your ass it works.