The first ever spin off game released on a handheld console was Pokemon Pinball for the Game Boy Color in 1999 since then there has been a rich variety of different releases from edutainment type titles like Learn with Pokemon: Typing Adventure and Art Academy, releases centred around electronic versions of the trading card game, pinball and puzzlers as well as a spin off generation of the traditional Pokemon RPG's in the forms of games like Pokemon Conquest and the Mystery Dungeon series.
Spin off Games on the Game Boy Color & Gameboy Advance
Spin off Games on the Nintendo DS
Spin off Games on the Nintendo 3DS