Pookas have appeared in Pac-Man games, so they are technically Pac-Man's enemies in Smash Run. Plus, Pac-Man represents all of Namco, as seen in his moveset. All enemies are from a playable character's franchise, with the SSE enemies being there because it is Super Smash Brothers, so even though the Sneaky Spirit could be there just to reference a franchise, it's very likely that Chorus Men/Man or some other character from Rhythm Heaven is playable.
(I have never played the Rhythm Heaven games, though, so it wouldn't really bother me much if there was no playable character, although the Chorus Men seem like they would be really unique if playable, being 2D like Mr. Game & Watch, so it wouldn't bother me if there was a playable character, either.)