As mentioned elsewhere, the girl in question DOES deserve what she gets. Joe shoots her in the behind with the staplegun (tack gun?). We get to see her wriggling her behind with a nice pattern on her behind. Then, Joe paddles those tacks in even further with the gun itself.
I recently checked out a Stooges video with this episode. Apparently it exists in several variations, the most recent one without the all-important scene.