So let's say I capture en passant with a pawn. Using the same pawn, I get to the 8th rank. Can I promote that pawn into anything else? I've heard of this restriction in various ways. Some say it can become a rook at best, and some say it just stays as a pawn, but it moves backwards.
Please let me know if this is a classic case of "I'm losing better make some stuff," or an actual rule.