What is Pokemon 102 in diamond and pearl?

Pokémon #102, in Pokémon versions Diamond and Pearl, is Cresselia, the Lunar Pokémon. Cresselia is #488 on the National Pokédex, which is the Pokédex that lists all known Pokémon thus far. Cresselia is a legendary Pokémon in both the Diamond and Pearl versions of the Pokémon game and only one Cresselia can be found in the wild in both games. For more information about Cresselia, visit the "Related Links" on this page under this answer.