>>35872983It's a music video for the at-the-time-current ending theme, Pocket ni Fantasy, which was sung by Sachiko Kobayashi and Juri Ihata. The song is about a little girl that wants to be an adult and her adult teacher that wants to be a kid again, and them bonding over Pokemon.
Kobayashi had been stunt cast in the first movie as the character Voyager, so they made a combined music video/movie trailer that had Kobayashi represented as Voyager and Ihata represented as some random little girl, then threw in an adult version of Misty to go along with the theme of the song since the video ends with a short voiceover by Misty promoting the movie.
That's all it is, the entire "lost footage from the movie" shit is just retarded Internet rumors.