Appearing before Pikachu and friends is the keyring Pokemon, Klefki. Inserting a mysteriously shaped key into the keyhole floating in the air, a very mysterious portal appears! Klefki has the key to go to various worlds. What kind of world will the key that Pikachu holds lead to?
Unfortunately the movie Pikachu, What's This Key? is not yet available on HBO Max.
| Directing | Kunihiko Yuyama | Director |
| Visual Effects | Ryo Sato | Animation Director |
| Crew | Satoshi Tajiri | Creator |
| Crew | Junichi Masuda | Creator |
| Crew | Ken Sugimori | Creator |
| Production | Tsunekazu Ishihara | Production Supervisor |
| Production | Masakazu Kubo | Production Supervisor |
| Visual Effects | Yōichi Kotabe | Animation Supervisor |
| Production | Mitomu Asai | Executive Producer |
| Production | Susumu Fukunaga | Executive Producer |
| Directing | Norihiko Sudo | Assistant Director |
| Writing | Atsuhiro Tomioka | Screenplay |
| Writing | Yuji Asada | Storyboard |
| Directing | Masakatsu Iijima | Assistant Director |
| Visual Effects | Sayuri Ichiishi | Character Designer |
| Visual Effects | Sayuri Ichiishi | Animation Director |
| Visual Effects | Kyouko Takeuchi | Animation Director |
| Sound | Masafumi Mima | Sound Director |
