I don't remember what street it was on, but I entered a street and started hopping along in the tree branches, when the screen seemed to freeze. I saw a speech bubble belonging to an unseen crab below me that asked if I would play music for the crab. Unfortunately, the lower half of the speech bubble was out of my field of vision, so I could not click it. And I couldn't remember if there was a shortcut key.
The problem was that I was completely frozen while the crab spoke to me; I couldn't move out of the tree (or even fall) to click one of the two buttons. I'm not sure what I did to get out of that bind; perhaps I hit the right key to play music, because suddenly I could move again. I'm not sure that I did hit that key to play music though, because it didn't show up in the local chat.