These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Pokémon 4Ever
Complete Monster: The Iron Mask Marauder is one of the few villains in this series who has absolutely no redeeming qualities, with the only other ones coming to mind being Pokémon Hunter J from the main show and Grings Kodai from the 13th film.
Deconstruction: Dark Balls really deconstructs the affect that Pokeballs have on Pokemon quite DISTURBINGLY.
Fridge Brilliance: In the beginning of the movie (40 years from the present), the poacher that was hunting down Celebi had a Scyther. Guess what Dark Celebi's monster looks like?
Related to above, Scyther wasn't random. Neither was Houndoom. Both their dual types are at the very least resistant to Celebi's attacks, and both are strong against Celebi's own dual types.
While traveling with Ash and co., the viewers see that Sammy has a passion for keeping track of all the different Pokémon he encounters in his sketchbook, and once they realize that Sammy is Prof. Oak, it finally makes sense where the idea for the invention of the Pokédex came from.