Adventure Time - Fin loses his arm

Formula for success:
1. Create a story with fun and colorful characters.
2. Add heartache, tragedy, or romance.
3. ???
4. Profit!

…what if we get to see it?
Like, what would that do to the show, could it ever go back to the lighthearted adventures of a boy and his dog after an episode where the main character looses his arm!?
Then again, the show has never really been all that lighthearted either, so it could work…