An idea for season 12. It contains 2 episodes.
The Joke/The Door:
Gumball gets pranked by Darwin and must apolagize to him. Gumball finds a creepy door that leads him to a weird place.
The Heartbroken/The Last Time:
Gumball gets heartbroken by Darwin. Gumball moves to a new place to stop the Robinson's to get annoyed.