Corrected entry: In both the theatrical and director's cut versions of the movie, right before Murphy gets killed in the vents, he calls out to the dog "Spike". Because in the theatrical version the alien incubated inside the dog, Murphy mistakes the alien for the dog. However, in the director's cut, the alien incubates inside an ox instead of the dog, but Murphy still calls out to Spike even though the dog doesn't even exist in this version of the movie.
Zvriith
14th Jul 2010
Correction: There could still be a dog, even if it was unseen.
JC Fernandez