Revealing mistake: In the shot where Celebi calls for help, its shadow disappears before it leaves the screen. (00:05:28)
Revealing mistake: When Professor Oak is getting a book from a bookshelf, the book appears out of nowhere. (01:15:52)
Pokemon 4Ever (2001)
2 revealing mistakes - chronological order
Directed by: Kunihiko Yuyama, Jim Malone
Starring: Eric Stuart, Veronica Taylor, Rachael Lillis, Madeleine Blaustein
Other mistake: When showing "In Association with" in the English dub's credits, The Pokémon Company is misspelled as "The Pokeman Company." (01:15:37)
Trivia: In the early reports when Movie 3 was still being made, there were rumors that Movies 3 and 4 were going to be interconnected, with Entei working with Mewtwo or something and then finding Celebi. Obviously, the creators abadoned this idea.
More questions & answers from Pokemon 4Ever
Answer: Missingno is a glitch from the video games, and is not a real pokemon, so no.
MasterOfAll