Mega Jump:

When you are playing with two players in Madden 64,
you can make a player fly. To do so, have the 1st 
player start pressing B to call audible as fast as
they can. The second player should press jump 
(left c) as fast as they can. The second player
will eventually jump continually on top of the 
screen. If you get him high enough, the instant 
replay will also be really screwed up.