Best sci-fi movie mistakes of 1976
Continuity mistake: When Logan and Jessica arrive at the ice cave, they are wet, so they take off their clothes and wrap themselves in animal skin to get warm. Jessica gets naked and Logan takes off his shirt but not his pants. But when they sit down we can see he is not wearing any pants.
Revealing mistake: During the scene when David is fighting off the large beast in the arena, there is a shot where you are looking right down its throat. Inside the "creature" you can see a light emanating from inside the mouth of the suit, probably so the actor inside could see while acting in it.