In Aliens, there is a scene when Ripley and Newt wake up and suddenly find two Facehuggers in their bedroom. It's obvious that Burke brought them there.
But the question is - HOW did he do that? Why didn't they attack him in the first place? They were in special glass containers. In order to achieve his plan, he should have been attacked by them when he first opened them. However, he somehow managed to bring them without any harm and noise into the bedroom...