Pokémon 4Ever/YMMV

Complete Monster: The Iron Mask Marauder is one of the few villains in this series who has absolutely no redeeming qualities, and with his horribly nasty actions towards Pokémon (Celebi and Suicune especially, not to mention the ones he Mind Rapes with his Dark Ball), children, and even members of his own team, he set the standards for true evil in the anime franchise.
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.
Harsher in Hindsight: The Dark Pokémon are based off the TCG, though nowadays Shadow Pokémon may come to mind.
- Though this might have been intentional on the part of Game Freak and Genius Sonority.
Ho Yay: There's quite a bit of subtext between Sam and Ash, though it becomes somewhat Squick-worthy when viewers find out who Sam is.
Moral Event Horizon: The Marauder dives over this when he captures and corrupts Celebi, making it create a giant vessel of destruction that he lets loose on the entire forest, all the while ignoring a fellow Team Rocket agent who's stuck in it and plotting to take over both Team Rocket and the entire world with his new power.
The Woobie: Celebi, so freaking much.