Continuity mistake: When the green snake slithers towards the boy, Todd throws a boot at the boys feet so the boy can hit the snake with it. The boy looks at Todd who motions the boy to hit it. The next shot shows the boys feet again, but no boot.
Continuity mistake: When Todd first encounters the humans on the waste disposal planet he falls down some stairs. He coughs up blood which is visible on his hand and on the ground. It cuts away from Todd and when it cuts back there is no blood at all.
Revealing mistake: When Todd is hitting the metal punchbag the first time, during the slow mo part you can see it flex as if it is made of rubber.
Character mistake: After killing three of the 'new' soldiers, Todd says that there are seventeen left. He then kills about another thirty.