He seems to be going through this phase where he is scared by seemingly harmless things. In California, he was terrified of this indoor play area because there was an air cannon that shot out balls and made a whooshing sound. So my boy, who ordinarily jumps into every situation with gusto, hid against my chest and refused to play. Later in the week he reenacted his fear with his stuffed bunny, saying that bunny was feeling "scared. balls." and we tried to talk about ways to help bunny feel better. I am really at a loss, other than just letting this phase run its course and assure him that I will keep him safe.
Luckily, all was not lost at the library. Paul was happy to participate in the craft, making a lovely set of red dog ears.