The official rules (e.g. Fide) actually say something like "Pawns can then be promoted to a queen, rook, bishop or knight." The general accepted rule whenever you are playing a game is that a pawn must be promoted to a PIECE, and as a pawn is not a piece this cannot be done.
On the promoting to extra queens rule- some sets are sold with extra queens. If these are not at hand, use upside-down rooks or, if no rooks are available either (and this HAS happened in my games against schoolmates) we use two pawns on a single square. If no PAWNS are available (it is fun tossing around the opposition, isn't it?) then, well... to be honest, your opponent should really consider resigning or something. If for some reason your position is still even (technically possible, though that would be an odd game!) then any token that isnt a chess piece would be fine.
dude its like you working 24 hours a day every day and making some hard work in which you can die. Then your boss comes to you and says I will promote you.. you will not be pawn anymore, you will be.. pawn!! Muahaha.. that would be making of you a fool, which isn't diserved as you worked 24/7.
Chess is like life ;)