The minifigure is split into two parts: the upper body and the legs, both of which are transparent, glow-in-the-dark green. The arms cannot move, but are stuck to the sides of the minifigure. The head is also fixed in one spot. In fact, the only spot where the alien can move is at the joint where the torso connects to the legs. There is a hole in the Alien's chest that makes it capable of holding any LEGO object that fits inside, such as its jetpack.
The chain of command for the Aliens is as follows: Drone, Saboteur, Commander, and Queen. It is stated that they are not from Mars, but came there to conquer it and mine out its Energy Crystals. They possibly could have crashed there, as seen in LEGO Battles (though that could have been a separate ship and they simply invaded Mars). They positioned themselves in the hive they built and are lead by Alien Commander, who is ultimately lead by the Alien Queen. They often carry staffs that can project an energy blast. Some of them wear jet packs (called Vipers) to move around the surface of Mars more swiftly.
In the end, however, they were driven off of Mars.
- In CrystAlien Conflict, they are not translucent, but instead solid green.
- What happened to the Martians that were there originally is unknown. It is possible that they were driven into extinction or went into hiding or Mars Mission could be set in an alternative universe from Life on Mars.
- It was jokingly said to be based of of the Sangheili species from the Halo universe. The face does bear a striking resemblance.
- 5617 Alien Jet
- 7644 MX-81 Hypersonic Operations Aircraft
- 7645 MT-61 Crystal Reaper (Two)
- 7646 ETX Alien Infiltrator
- 7647 MX-41 Switch Fighter
- 7648 MT-21 Mobile Mining Unit
- 7690 MB-01 Command Base (Four)
- 7691 ETX Alien Mothership Assault (Five)
- 7692 MX-71 Recon Dropship (Four)
- 7693 ETX Alien Strike (Two)
- 7694 MT-31 Trike
- 7695 MX-11 Astro Fighter
- 7697 MT-51 Claw Tank Ambush (Two)
- 7699 MT-101 Armored Drilling Unit (Two)