The most surprising zoo encounters I've had are at Woodland Park Zoo in Seattle. The first time I visited I was very young and we'd taken a trip over from Eastern Wa. I was sitting on a bench alongside a path, my step sister was looking at me smiling and I didn't know why. Apparently she had set me up for a regular occurrence that happens there. A squirrel came running across the path out of my line of sight, then jumped up on the bench, then on my shoulder opposite the arm I was holding a peanut in, then ran across my shoulders, down the other arm, snatched the peanut, and ran off. This all happened before I even saw the dang thing.
I think it was that same day I also made the mistake of leaning against an exotic tropical bird cage, hanging one fingertip slightly through it. The bird hopped down and bit my finger with the point of it's very sharp beak, thinking it was a nut or something. It was very painful, but lesson learned.
My other encounter was after we'd moved to Western Wa, and I was living on my own. I was admiring the Peacocks. Little did I know they sometimes get overexcited and show their feathers to humans. Like a dummy I stood their admiring him, not realizing he was trying to court me. When I walked away, he started following me. I then took off running just for laughs yelling "Help". The thing sprinted after me making a loud wailing sound. The zoo staff just laughed.
There was some local petting zoo I went to on a school field trip come to think of it when I was even younger in grade school. I bent over to pet one animal, and a male goat took the opportunity to put his head down, charge me, and bash me in the butt and knock me down. Those things are very strong and fast even when they're young. His strike hit my rear so hard it made me pretty sore for a while. All the kids and even the teacher were just laughing. I'm like, thanks a lot guys, I'll just stand for a while, I'm too sore to sit down.