Action Girl: Marina may be a ditz, but she's quite competent as a trainer.
Adaptation Dye-Job: In order to fit with the character, Marina's design was recolored from her game counterpart's to look more girly than tomboyish (pink instead of red, blue rather than yellow, light blue hair instead of dark blue hair, etc.)
Adaptation Name Change: Arguably, Kenta/Jimmy and Marina. Other characters based on Player Characters have their names based on one of the default options (Satoshi/Ash, Shigeru/Gary, Haruka/May, etc.), however Kenta/Jimmy and Marina's names don't come from the game at all. (If they did Kenta/Jimmy would be Hiroki/Hiro and Marina would be Chiho/Amanda.)
Ascended Extra: Professor Sebastian, a One-Scene Wonder in the special, went on to become a more important character in the later Lake of Rage two-parter. A Rocket agent working under him there even has the same type of uniform as Attila and Hun.
Bit Character: Kudo. The man has, what? Two minutes of screen time total? About half that in the dub considering that they cut the whole epilogue. (Yet, he somehow earns himself his own eyecatch...)
Broken Mon: Raikou. It's... leery of humans. Being continually molested by Team Rocket can't help matters.
Dub Name Change/Dub-Induced Plot Hole: Jackson is renamed "Vincent," and Eusine is renamed "Eugene." Keep in mind that both characters retain their Japanese names (Junichi and, as mentioned above, Minaki).
Electric Torture: While Raikou does get shocked a lot, it at one point is also forcibly and painfully drained of its own electrical power.
Elsewhere Fic: A canon example; Ash and his friends do not appear.
Fangirl: Marina is a total Lance fangirl. Or as she calls him in the dub... Fabu-Lance!!
Lower Deck Episode: Other characters besides Ash and those he knows are the main characters for this special.
Million to One Chance: When the Black Hole Crystal activates, Eugene explains to Jimmy and the others that their only chance of saving Raikou would most likely become a suicide mission if not timed to the right fraction of a second.
Moment Killer: Vincent is this when Jimmy and Marina are making eyes at each other at one point. Justified however considering that they were still in danger from the villains, and Marina was still sitting on his back after falling several feet from the air.
The Stoic: Hun's only visible emotion can only be described as "bloodlust". Anything else and he maintains a bored facade.
Took a Level in Badass: Vincent. In the Johto Silver Conference (where he went by the name "Jackson") he was able to fight Ash to a draw, though he kept the silly attitude and clumsiness.
Marina also has non-speaking cameos in the "Diamond and Pearl" series, once on a watch advertisement and the other in footage of her appeal in a contest, where she's known as one of the world's best coordinators. Seeing as she wanted to be an idol trainer, this makes her one of few characters to succeed in her goal.
Unknown Rival: Jimmy really doesn't consider Vincent a rival at all, at least in terms of vying for Marina's affections.