I got 2 angry yellow jackets stuck in my helmet the same week, each stung me a couple times, one on top of the other sting, it was so swollen you could see my blood pulse underneath my skin.
Other than that, I had a squirrel jump and get caught in between the pedals of my fixie a couple years back, I lifted my feet out of the way and fought the pedals until it jumped off, even with my hands firmly on the bars, I got a serious case of the wobbles from that.
As for why deer run in front of traffic, I did a bit of research on this a while back, the theory is that if you're being chased by a predator, you have have the greatest chance of escape if you can make the predator start running after you start running. Deer do this by making the predator need to change its acceleration vector by the greatest amount. By running across the predator's path, the deer will cause the predator to overshoot and need to turn around an acute angle to get to the deer where as the deer can leave at a constant acceleration. This effectively gives the deer a head start.
At the speed cars and bikes go, this doesn't give the deer enough time to make this strategy work. Since the car/bike isn't (normally) in pursuit of the deer, the deer crosses the car/bike's trajectory at the same time as the motor vehicle.