In the movie Stalag 17, animal (robert Strauss) slips in the mud while running to see the new Russian prisoners. He lands on his rump, gets up and continues to run less his shoes to the wire. His backside is covered with mud. In the next series of scenes he attempts to cross the wire to get to the prisoners and falls in the mud again --this time face first. He gets up again and lo and behold he is covered with mud in the front -- BUT NOT ON HIS BACK. Where did the mud on his back go?