"Didn't your mother ever teach you to share, Snivelly?" ...If she had she was a leg-up on Sirius's own mother, but that's beside the point. "You only wish-"

We'll never know what Snape would only wish, in Sirius's opinion, as at this point the frustrated couchrodile, dismayed at having ropes around its face, thrashes expansively. And thoroughly.

Sirius is saved the worst of it, crouched behind his dresser, but other items of furniture go flying. Snape is actually not in a bad position by the beast's head and is spared the whip-crack violence of the tail, but it's writhing still slams its head and shoulders into him. ...Where were all those potions materials again?

Sirius wisely assists everyone by casting a slicking jinx on the floor, making it extremely slippery. And chuckling quietly. Ohhh this was a proper mess.

"Anytime you've had enough, feel free to apologize!"