Corrected entry: How did the stowaway facehugger impregnate the dog (or ox, depending on which version of the movie) after it had already impregnated Ripley with the Alien Queen? Alien 1 & 2 had already established that facehuggers die shortly after impregnating a host. Not only would it be impossible for the same facehugger to impregnate 2 hosts, but it should have died after impregnating Ripley.
Teru_Kage
11th Jun 2013
Correction: The Facehugger that impregnates the dog/ox and Ripley is a much stronger breed known as a Royal Facehugger, which is able to impregnate two victims and does not die until both of them are impregnated - http://avp.wikia.com/wiki/Royal_Facehugger.
THGhost