When playing you might have noticed, with the combat androids, you can destroy their head completely and they will still keep functioning. Now that's not too strange, considering they are just robots, but I found a weird side effect!
If you are playing as the Alien species, or Predators, you can do finishing moves. That is when you press the interact key and get a guaranteed kill. Several of the finishing moves on humanoids with both these species involves decapitating the head.
Now, if you decapitate an android via general combat AND THEN pull off a finishing move, it can have an interesting result. First it will preform the animation as if the head is still there(slicing, whacking, stabbing, ect at the place where the head should be), then, the androids head will reappear! The android should then be dead, but appear totally undamaged.