I just had that odd ball attack too, my guy has used the knockdown signature move for a lot of fights and then today i get this out of no where:

REEKO runs madly around the arena.
REEKO tries to strike his opponent.
REEKO looks to stun PANDANSLESDENTS with one of his signature moves! (-Signature Move: Stun-)
REEKO's attack lands on PANDANSLESDENTS's armpit causing magnificent damage! (+172 Damage)