I had received the Best Minion Ever quest, but I was still working on the various other Southern Bay quests. I had completed the Bad Hair Day, but was waiting to catch up to ClapTrap before I turned it in.
When I got to ClapTrap's boat after killing Flynt, he just kept dancing, and I couldn't turn in either quest (or travel at the back of the boat. I figured all I could do was restart the session, and that let me turn in the Best Minion Ever mission (and travel to Three Horns.)
ClapTrap disappeared into his boat at that point, and I wasn't able to turn in the Bad Hair Day mission. When I finally got to Sanctuary, I tried trading with him a couple of diffeerenet times, and he was either unresponsive, or giving/receiving missions and turn-ins, but not for bad Hair Day. Finally, I just gave up, and turned it in to Hammerlock, instead.