I've seen a lot of strange stuff on the road: Bison, caribou and resting camel, apparent picnickers causing a traffic jam, a (pretty awesome) stripshow in the cab of another semi, on the I-95, and etc. Heck, in Saudi you'd occasionally see new Mercedes' apparently abandoned on the side of the road because they had a flat tire.
To me, one of the most impressive things I've seen may have been a single deer crossing the I-20. It jumped the fence on the side, crossed two lanes of pretty heavy 80mph traffic, ran through the lightly wooded median, crossed two more lanes of pretty heavy 80mph traffic, and jumped the fence on the other side of the highway.
That deer was damn amazing, perfect timing, bobbing and weaving through traffic. I don't know what was on the other side of the highway, but that animal earned it, whatever it was!