A mellophone is what french horn players march and play in marching band. It's like a trumpet with a horn bell. Trumpet players call it a trumpet on steroids. But really, a trumpet is an anorexic mellophone.
Trumpet Player 1: Man! What is that thing?!
Trumpet Player 2: It's a mellophone. AKA a trumpet on steroids.
Trumpet Player 1: Ohhh! That's funny!
Mello Player: Really??? 'Cause I heard you play an anorexic Mello??