|Home world:||Planet Plachiku|
|First appearance:||Ultraseven Episode 30: "For Whom Takes the Glory" (1968)|
Subtitle: Plastic Phantom (プラスチック怪人 Purasuchikku Kaijn?)
- Height: 40 m
- Weight: 15,000 t
- Origin: Plachiku star
Alien Plachiku first appeared with his fan-like drill under ground after it was detected, but soon got away after the latest Ultra Garrison member tried to glorify himself. Later that day he managed to hijack the TDF MRI with four tanks and went on a rampage. With the tanks shortly destroyed by the Ultra Garrison, Dan sneaked aboard, but was seemingly knocked out by Alien Plachiku until he turned into Ultraseven. The two of them grew much larger and battled, but after being tossed Alien Plachiku seemingly surrendered until Ultraseven turned around and was petrified. Alien Plachiku continued his attack when Ultraseven became unpetrified and destroyed his drill with the Emerium Ray. After some time of fighting both fighters became very exhausted and could barely crawl until Ultraseven tossed Alien Plachiku and destroyed his body with the Emerium Ray. Later on his skeletal form was killed by a shot from the Ultra Garrison.
- Magazines released at the time of the episode's release stated that Planet Plachiku is made entirely of plastic.
- Although not physically seen, Alien Plachiku is one of the monsters that makes up Beryudora's Left Arm in Mega Monster Battle: Ultra Galaxy Legend The Movie.
Powers and Weapons
- Drill: Alien Plachiku can control a giant fan-like drill similar to the Ultra Garrison's TDF MRI. This vehicle launches grenades and can petrify pilots.
- Petrify Mist: Alien Plachiku can release a mist from his "mouth" that petrifies enemies on contacted, however, this mist only has a limited amount of time on Ultras.
- Extraordinary Jumper: Alien Plachiku can jump far distances.
- Skeleton: Alien Plachiku can revive himself in his skeletal form.