In the movie Pokémon Heroes Latias is able to transform into Bianca (a human character in the movie). Serebii.net, however, does not list transform as a move Latias can use. Were any comments made in the movie regarding the transformation? Is Latias using the move transform or is it using some other power?
According to Bulbapedia, in the Pokémon Adventures manga, Latias is also able to appear as a human by using its ability to refract light. This is consistent with its Pokédex entry in the Sapphire game: