Alien, Tower Defense Simulator Wiki

The Alien was the first Area 51 enemy that spawned in the event. The Alien had the same speed as the Normal, but had more health than it. It is the weakest enemy that spawns in the Area 51 Event. The Alien's appearance was similar to an extraterrestrial enemy. It had a stereotypical green body with a rounded green alien head. These are rather easy to kill, so Crook Bosses or Minigunners can be used to kill these. A well placed Pyromancer can also kill this. Since they spawn in hordes, Rocketers

Celestial Pillars - Official Terraria Wiki

Fourpapa1 - Builder Portfolio - Portfolios - Developer Forum

Forerunner - Species - Halopedia, the Halo wiki

Alien Shooter TD on Steam

Area 51 Event, Tower Defense Simulator Wiki

Glitched Giant, Tower Defense Simulator Wiki

Green goblin

Achievements and Trophies - Aliens: Fireteam Elite Guide - IGN

Nuclear Monster, Tower Defense Simulator Wiki