How it begins is even more hilarious. Unlike other punishments, this one is sprung onto him at the last second. They had Murr believe they were doing a normal challenge by teaching students what to do when they skydive. Once they surprise Murr with the revelation that this is his punishment, cue him taking off his jumpsuit and storming off to their van before they drag him inside. He didn't have the key though.
For the people who felt sorry for Murr at the end of Human Pinata and Look Out Below, Joe getting his LaserGuidedKarma at the end of the ep No Escape. You notice at the end they left him alone on stage the same way they left Murr alone at the end of Human Pinata.
In the ep Nationals Disaster, Joe's pathetic attempts at gymnastics are so hilarious it causes BOTH Sal and Murr to fall down.