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 |
| Production | Tsunekazu Ishihara | Production Supervisor |
| Sound | Masafumi Mima | Sound Director |
| Crew | Junichi Masuda | Creator |
| Writing | Yuji Asada | Storyboard |
| Directing | Masakatsu Iijima | Assistant Director |
| Production | Masakazu Kubo | Production Supervisor |
| Directing | Norihiko Sudo | Assistant Director |
| Visual Effects | Sayuri Ichiishi | Animation Director |
| Visual Effects | Yōichi Kotabe | Animation Supervisor |
| Production | Mitomu Asai | Executive Producer |
| Writing | Atsuhiro Tomioka | Screenplay |
| Crew | Ken Sugimori | Creator |
| Visual Effects | Sayuri Ichiishi | Character Designer |
| Visual Effects | Kyouko Takeuchi | Animation Director |
| Production | Susumu Fukunaga | Executive Producer |
| Crew | Satoshi Tajiri | Creator |
| Visual Effects | Ryo Sato | Animation Director |
