What if David is still around during the original trilogy era, using engineer tech to spread his creatures wherever he can.
After the events of Aliens, he gets wind of how many of his babies Ripley and co. wiped out on LV-426. (Maybe he's somehow able to monitor the situation through Bishop.)
So he seeks revenge, boards the Sulaco, and places an egg above the cryotubes.
Imagine if Alien: Awakening managed to tastefully pull that off.