Crusade Pikachu + Extra versions
It's Pikachu with the assets from Super Smash Bros. Crusade. It isn't just a simple resprite, because frame count, sprite number and even some moves are different from the vanilla version.
There are also different variants which have Ash or Red in the background added in as an extra.
Put the data file into your SSF2's data folder and don't forget to make a backup.