You were taking a stroll around Nostromo and came up on a Xenomorph that is brutally injured. You felt sympathy for the creature and you decided to get your acid-proof vest on and some acid-proof equipment to start helping the Xenomorph back into shape, with metal and other stuff, putting new arm and leg for it. For that, the Xenomorph looked at you and purred, as it earned your trust. It slowly placed it's head onto your hand.