Interesting crossovers to do with Howl's Moving Castle:
- Sullivan from Monsters, inc. I blame
fujurpreux. It's all about entering the wrong doors.
- Fujimoto from Ponyo on the Cliff. They were ttly interdimensional BFF before this guy moved out to the sea in disgust to his own species.
- Just Discworld. You know Howl can also move through L-space. Let's argue with the Librarian and fellow coward Rincewind!