H.R. Giger’s design remained practically unchanged by the Alien FX team at Stan Winston Studio apart from adding two tiny arms to create consistency between it and the anatomy of a full grown Alien Warrior. Cameron and Stan Winston decided that the addition of arms also made sense on a purely functional level, allowing the chestburster to pull itself free from its victim’s chest.
- Stan Winston School
You can read up on more details about the Chest Burster Mechanism here. There’s plenty to learn about it’s multiple appearances across the franchise and what techniques were employed to pull off the effect.
It still makes me shudder. So cool, yet so creepy.