Nintendo studio Brownie Brown helped make Mother 3. It also, quietly, made a Professor Layton role-playing game, available only in the Japanese and American versions of DS game Professor Layton and The Last Specter.
Japanese developer/publisher Level 5 have unveiled a brand new title today. Called Fantasy Life, it's a game for the DS that looks a little, well, familiar.
GameBoy Advance Mother 3 sadly never got a Western release. That doesn't mean it couldn't possibly get a DS release.