Pokémon Heroes: Latios and Latias is the fifth in the series of Pokémon movies and the first not to have a number in the title. it tells the story of Ash and friends' visit to the Venice-like city of Altomare, where they take place in a water chariot race, and later meet an aspiring artist named Bianca, and her grandfather who runs the city's museum. The two of them hold a secret: the knowledge of Latios and Latias, twin dragon Pokémon who protect the city and the Soul Dew, a mystic orb that keeps the city safe from natural disasters. When a pair of thieves, Annie and Oakley, come to steal the Soul Dew and revive the ancient Pokémon at the museum, it's up to Ash and his friends, as well as new allies, to stop them.On a side note, this was the final film with the original cast (Misty is not in the next film), as well as being the last movie to get a theatrical release in the U.S. until Pokémon the Movie: White - Victini and Zekrom got a one weekend limited release in 2011.
Deconstruction: It's notable that this film takes a much different approach to most Pokemon films: The opening contest (where the theme is sung) isn't a Pokemon battle, Ash loses said contest, battles take place in real-time and are always on the move, a heroic character is Killed Off for Real, etc.
Expy: Altomare itself is this. How many people could look at it and not say "That's Venice!" Seriously, the plaza two pillars that the statues of Latios and Latias are on is pretty much an exact clone of the Plaza of St. Marco! The film crew very clearly based Altomare off of Venice.
Fix Fic: At least one fanfic has Latios being brought back to life.
Magic Skirt: Bianca, and Latias while disguised as Bianca. (Though, admittedly, it's justified in the latter's case.)
Meaningful Name: Annie Oakley was the stage name of Phoebe Mosey, a famous American exhibition sharpshooter. Also regarded by many to be the first "superstar" for having starred in Buffalo Bill's Wild West stage show.
Mind Screw: Either Bianca or Latias kissed Ash on the cheek in the end. We have no exact proof which it was, because Bianca's major distinguishing feature from Latias is wearing a hat, and the hat was left in Bianca's house. General fan consensus is that it's Latias, though; Bianca showed no signs of attraction to Ash (or even interacted with him much).
Missing Trailer Scene: The original Japanese trailer had almost nothing from the final movie. Examples include a reanimated Kabutops skeleton, some sort of red energy monster emerging from the Defense Mechanism, and the gang standing around a glowing Soul Dew INDOORS, with no sign of Latias. Shame - that Kabutops skeleton looked awesome.
Moe Couplet: Ash and Latias have this trait in abundance. Despite the obvious Interspecies Romance, their interactions are so sweet and cute that AltoShipping is still a rather popular couple in the fanbase despite the movie having come out back in 2002.
Pet the Dog: Annie and Oakley do really care for each other, and (after realizing things have gotten out of hand) Annie actually smiles when Latios is rescued from the machine toward the end of the movie. Also, Annie has an Espeon, which only evolves at maximum happiness.
Scenery Porn: Again, Altomare is an Expy of Venice Frikken' Italy! There are a lot of chase scenes just to take advantage of that fact.
Unnaturally Blue Lighting: There is an obnoxious blue tint given to 90% of the movie in the English DVD release. It's very distracting. At one point in the movie, Misty mentions that "it's so blue."
With Great Power Comes Great Insanity: When she gets into the Defense Mechanism's cockpit, Oakley goes a little Off the Rails and nearly destroys the entire city. It seems to be actually induced by the combination of the machine and the Soul Dew, as when it's trashed, she literatelly snaps out of it and can't remember what she was doing.