I have no idea which episode it was, but it was referred to specifically on
Lisa goes to a nature activist meeting and the leader of the meeting, a handsome boy with dreads, tells the group that they need a volunteer to stay in an endangered tree. He says "This means once you're up there, you won't be able to come down for anything. Not for a Phish concert - not even for Burning Man."
Thanks to Addis, I had more free time.