From IMDB: "Pokémon: Giratina and the Sky Warrior" is the English title for the eleventh theatrical movie spin-off from the popular Pokémon TV series. The movie's basic premise centers around the existence of a "Reverse World," a kind of alternate universe designed to correct imbalances in the "Real World." Five years before the events of this movie, a research scientist named Newton Graceland apparently discovered the Reverse World and its sole resident Pokémon, Giratina, a winged, six-legged, metallic dinosaur-like creature. Newton and his assistant Zero plot to harness Giratina's power and take over the reverse world.Series regulars Ash, Dawn, and Brock, along with their regular Pokémon companions, get roped into all this through the intervention of a cute, grassy little Pokémon called a Shaymin, who's on its way to the "flower garden" for the "flower-bearing" ritual with other Shaymin. Shaymin can communicate telepathically so we can hear its articulated thoughts, making it one of the very few Pokémon who can actually "talk". Shaymin's connection to Giratina and the Reverse World has something to do with its ability to render toxic material harmless via some internal process. Giratina seems to need Shaymin's help. In the end, Newton, who enlists Ash and his friends to help him, finally figures out what Giratina wants.
Ambiguous Gender: Shaymin, even for a "genderless" legendary. In Land Forme, it speaks with a soft, feminine voice (and in Japanese, uses feminine pronouns); in Sky Forme, it is headstrong and speaks with a much more masculine voice (and accompanying Japanese pronouns.)
Zero: *after Newton deletes the blueprints to the Megarig* How could you..PLEASE...DON'T DISAPPEAR!!
Newton: Leave it be, Zero...this is how it should be. We cannot sacrifice Giratina for the sake of our research. Please understand, Zero!
Zero: *crying* All...All I wanted...I hate this polluted world...I just wanted to stay in the beautiful Reverse World...That's all...
Cloud Cuckoolander: Newton, at least Ash and Dawn seem to think so. It's heavily implied he's been floating around the Reverse World for years — he's physically identical to himself in Zero's memories.
Decoy Protagonist: Without dying, but who thought Dawn was the main character in a movie with a cute little fuzzy thing?
Determinator: Zero and Newton are both this in their own ways regarding the Reverse World.
Disney Death: Giratina pulled that off. Luckily, Aromatherapy doesn't just cure all the status ailments in your party, it also brings Olympus Mons back to life!
Giratina was still breathing prior to Aromatherapy, but it still contributes to the trope.
The actual moment of the trope is actually the reveal that Giratina is breathing: Pikachu and Piplup react so dramatically to Giratina's fallen form that the cast assumes the worst... until Dawn notices the dragon's neck moving.
Early-Bird Cameo: Giratina's Origin Forme and Shaymin's Sky Forme, ahead of the release of Platinum. Although the movie was supposed to be the proper debut for Shaymin, if it weren't for hackers discovering all the Generation IV event Pokémon beforehand.
"Groundhog Day" Loop: Dialga traps Giratina in one of these so it can escape the Reverse World without the latter following it.
Harmless Freezing: Zero is frozen inside of the Mecha Giratina for an unspecified amount of time, but appears completely fine when he is recovered and doesn't seem to have been affected by the cold; this may be due to the thick suit he is wearing
Insufferable Genius: Newton brags about how he is a genius (if he does say so himself) and it shows in his Crowning Moment Of Awesome when he shuts down the entire Megarig. He also shows some pretty Badass skills while piloting that Airbike, avoiding attacks all with two kids along for the ride.
Involuntary Shapeshifting: This happens to Giratina whenever it leaves the Reverse World or returns to it, and to Shaymin when it comes in contact with the pollen of Gracidea flowers (as well as when night comes or it gets encased in ice if in its Sky Forme.)
Newton Graceland's Japanese name is Mugen, which means 'infinite', while his English name may come from the scientist Issac Newton, who developed the concept of gravity. The last name 'Graceland' is a play on the Gracidea flower garden.
Then you have the holographic maid in Zero's ship, Infi, whose name is also a shortened form of infinity; her character design also incorporates lemniscates.
Mirror Universe: The Reverse World. Supposed to be an Pokemon equivalent of an antimatter universe.
Could be that antimatter things are turned into normal matter or vice versa when traveling between worlds.
Split Personality: Shaymin in Land Forme is cowardly, rude, and ungrateful, but when it changes to Sky Forme, it becomes brave, adventurous, and headstrong, almost like it becomes an entirely different Pokemon (he's still keen on being thanked while not thanking others, though).
Tender Tears: Shaymin Land Forme at the end of the movie. As if it weren't adorable enough.
Tsundere: Shaymin is a Type A to Ash for the majority of the film.
Villainous Breakdown: Zero appears rather calm and collected at the beginning of the movie, but after he captures Shaymin and uses it to open a portal using Seed Flare in order to allow Giratina access to the real world again so he can put his evil plan into fruition, he starts showing a dramatic change from being almost stoic to going off the deep end by the climax of the movie.
He also had an even BIGGER breakdown in the manga version.
Well-Intentioned Extremist: Zero thinks that by destroying the real world, he's saving the Reverse World (which he plans to achieve by causing massive property damage in the Reverse World itself). This causes him to nearly murder the guardian of the Reverse World in the process.
What the Hell, Hero?: This is the reaction Ash and Co. have when they find out that Newton designed the Megarig.
White Hair, Black Heart: Zero is this to an extent. He has no problem with killing Giratina for the sake of his own wants and needs, but he honestly thinks that the Reverse World is being polluted by the real world and wants to 'save' it.