One night on the Fantasy, I saw Captain Hook and Smee ready to take some pics. So I got in line for my first-ever cruise character pic and then politely informed the Captain I only wanted one with his first mate, who's always been a favorite. Well, I didn't take into account Hook's ego and he stomped off - completely. I stood there astonished, with a whole bunch of other cruisers wondering what I had done. It still makes me smile (although maybe not so true for the passengers who wanted Hook's pic!)
And at WDW, I once went to a reception for my company where Chip 'n Dale were in one corner available for pics. It wasn't really the crowd for it, so I think they stood there for ages with no one. I happened to glance over right as they noticed me, and they began waving and jumping and being generally adorable, so of course I had to go over. They proceeded to fight over who got to take the first pic and hold my arm and just made me laugh so much - aka best part of the night for me.