If you loved Mount Head, try One Piece: Take Aim! The Pirate Baseball King
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
What they share
Theyboth carry the playful mood tag, and they sit in Animation / Comedy / Fantasy territory. If that's the register that drew you to Mount Head, the second film will land in a comparable space — through a different lens.
playful
What One Piece: Take Aim! The Pirate Baseball King is
A baseball game hosted on a floating stadium seems like a fine way to break up piracy. A crew of pirates faces off against the Arlong crew in a high-stakes match, complete with spikes on the ball. They still find time to hit actual bases between attempted murders.

