Joke's on you, Sitch!

On Thursday's all-new episode of MTV's Jersey Shore, Pauly D and Vinny Guadagnino take it upon themselves to clean up the shared bathroom the roommates share in Florence, Italy, but the room's final sparkle didn't come courtesy of Mr. Clean.

"The bathroom is disgusting and there is this disgusting toothbrush on the counter," says Pauly. "I'm getting all the nasty hair out of the clippers and used someone's toothbrush. Anyone dumb enough to leave their toothbrush on this counter deserves it."

So who's the brush's rightful owner? None other than an oblivious Mike "The Situation" Sorrentino, who promptly walks into the now-clean bathroom and starts brushing his teeth.

Reasons Guadagnino, stifling laughter: "Part of me feels bad, but then I'm like, 'Yes! This is awesome!'"

Watch more of the guys' prank in the clip above before the full episode of Jersey Shore airs Thursday at 10 p.m. (EST) on MTV.