A family was driving near the Mammoth Hot Springs area of Yellowstone National Park when they realized there were others on the road. Not just vehicles, but also a lone howling gray wolf that was holding up traffic.
It's hard to impress a bison and not necessarily safe to try. You can ask a group of snowmobilers who just recently traversed Yellowstone National Park in a snowstorm. No, the bison they encountered was not impressed.