Thanks to TV Tropes, I'm convinced it's a visual pun: she's "slytherin" on the floor.

*dodges inevitable rotten fruit*

And I'm not sure if A Very Potter Musical is canon puncture or not. I mean, obviously it is, but everyone's so different from their book counterparts, partially because some characters were condensed so it'd be easier to play. Draco was essentially combined with Luna Lovegood and I bet a bit of Viktor Krum since he had a crush on Hermione.

"I want Hermione Granger! And a rocket ship."