When Marn meets the old man at the beach, he puts on the same boot twice.
Marn blows a hole straight through the swamp creature's stomach. When the creature falls to the ground, it has no such wound.
One of the mutants who chases the girl is wearing sneakers.
A cameraman's shadow is visible on the ground during one of Marn's first battles with Clon.
During the final battle between the heroes and Clon, briefly you can catch the camera man's thumb over the lens in the upper right hand corner.