I found the meaning of 'mullet' in dictionary and it's a fish..? Does it mean a real fish what they are saying in this video about Ezra's hair ..?
Ezra is trying to describe his haircut.
As the guy in the baseball cap says:
I know for a fact that growing the back out..., it's mullet style
but this is Ezra in the movie Fantastic Beasts and Where To Find Them
with the mushroom cap he mentioned.