Clefairy randomly appears from a thrown Pokeball in Super Smash Bros. and Super Smash Bros: Melee. In SSB, Clefairy uses a random special attack from one of the other Pokémon that can appear from the Pokéball; in SSB:M, it uses one of four preselected attacks, including a self-destruct.
A glasses-sporting Clefairy is the adorable "Teacher Pokémon" in the Pokémon Stadium minigame "Clefairy Says," seen in the above video.
You can witness an in-game version of the Clefairy Dance in Pokémon SoulSilver, as seen above:
