Green colored rats that can only be spawned by a Big Green Rat. They are similar to regular rats, but they don't drop rads and have less HP. However, green rats do drop pickups, which means that this enemy is great for farming ammo or health via Rabbit Paw or Blood Lust. They die on their own after 30 seconds from being spawned.
- In the game code, Small Green Rats are referred to as "Fast Rats".