'Design a Character that fits into one of the Seven Archetypes'

Ok so I'm 100% sure i wanna do Finn my cute little fish :)

here's a pic of him 

I'm now writing out my character sheet, thinking about his background, his likes dislikes, what's his goals etc...

I also need to pick an archetype for him. We had a presentation on them which was instructive and interesting. I can choose one of these seven. Shadow, Hero, Trickster, Shapeshifter, Herald, Guardian and Mentor.

Since i've been looking at minion alot and watching megamind ALOT. I kind of wanted to go down the route of the guardian. But seen as Finn is a companion and he transforms when he's angry he cant really be a guardian because there supposed to keep there cool. (like minion does) But cause he gets out of control he's got to be a trickster. Someone who can be mischievous and have a humor element. I think Trickster suites him very well.

Here's my character sheet of him