i believe nothing is wrong with his hat, he simply just wears it, and hides his golden LONG hair. as shown in the episode, how to cut a womans hair
you can get a Finn hat or a Jake hat at Hot topic
Finn's hat is sort of a bear skin, I read in the adventure time wiki and set on the character and clicked Finn it said it is a bear
He always wears his hat because it's awesome, but took it off a few times. :)
You can buy one at hot topic
Finn takes his hat off in "To Cut A Woman's Hair" (season 2, episode 10)
I added some links to sites that sell them.
Go to YouTube and search Finn Hat DIY. He explained it really well. Or you can buy one from Frederator Blog. :)
Pen is one of the main characters of the show, he's the boy with the hat and backpack. He was later renamed as Finn.
Because Pendleton Ward wanted it that way, what does it matter.. ? It's like asking why Finn's hat is white... it just is...
He has blonde hair.
to keep his hair under control while fighting
possibly because she never answers finn when he asks if she is human or not when she appears in the episode ''susan strong'' and in the new episode '' susan returns'' when finn's hat comes off she notices he does not have fins