I gotta go with Groose, he's got good character development, its funny to see his reaction when Zelda chews him out, he helps you out later and he delivered such verbal gems as
"leave my doo outta this!"
and
"let's call it Grooseland!"
As far as bullying goes Groose is the meaner one, he steals your bird, he throws stuff at you in the competition, he insults you, he leaps on top of Link from who knows how many feet in the air which coulda killed them both.
Mido comes across as more of a whiner then anything else