Not that it ruins my enjoyment of the movie, but I'm curious about the scene in BTTF2, where a postman shows up in 1955 where the Doc had been blasted back to 1885 and gives Marty a letter that the Doc had posted 70 years earlier.
Would the Post Office would really agree to this? It seems like a very strange request - i.e. "Deliver this letter in 70 years to this location" which is not even an address, just somewhere on the side of the road which we can only assume exists in some form in 1885. It also seems logistically difficult, they'd have to keep the letter in a file somewhere through several generations of staff and still be sure that it was delivered at the appointed date. Do they have a system to do this kind of thing?
(The postman doesn't seem too surprised - he laughs it off, basically just saying he'd lost a bet.)