On the day before Christmas, Pikachu and its Pokémon friends are playing in a snowy town. But their snowball bowling game goes awry, and Totodile's snowball knocks a passing Delibird out of the sky! Delibird crashes down onto Meowth and Wobbuffet, who were out for an innocent stroll, but a wild Skarmory is annoyed at the racket and sends them all blasting off. Delibird has another bumpy landing, and now it's in a panic because it's lost all the presents that were in its sack. If they're not found by midnight, they won't be delivered for Christmas! Fortunately, Pikachu and its friends will help Delibird find all the presents.
Source: The Pokemon Company