Mark showed up at the Yosemite facelift, invited because they didn't have a campground, not a participant and did nothing but bitch.
"What's with this Facelift thing?"
"Can you keep the music down?"
"Are those drummers going to play all night every night?"
Basically being his curmudgeonly self...
I had people come up to me for days after, asking: "Who was that guy complaining about everything?"