Subtitle: Nomadic Alien (遊牧星人 Yūboku Seijin)
At some point in the past, the Simons had been attacked (and possibly controlled) by Yapool. As part of his plan to defeat Ace once and for all, Yapool impersonated a juvenile Alien Simon to evade detection. He first pretended to be targeted by Yapool in order to get closer to TAC. He later escorted some kids away to safety when Jumbo King attacked the city. Despite talking only in his kind's language but later he told Hokuto via telepathy that he is a Yapool in disguise and his true plan was to getting his revenge on TAC and Hokuto, and depriving the children's kindness. He was finally defeated by Hokuto, shortly before he transformed into Ace. With Jumbo King soon defeated, Yapool was forced into hiding, but kept on scheming in his own dimension.
- Simon's suit was modified from Alien Antira.
- The real Alien Simon never appeared as this one is just an imitation of Yapool.
- Like Yuko Minami and Aprasar, Alien Simon's race was also endangered by Yapool.
- Simon's name may refer to being Psychic, as Simon communicates primarily through telepathy.
- Height: 199 cm
- Weight: 80 kg
- Origin: Planet Simon
- Powers and Weapons
- Shock Rays: Alien Simon was theorized to possess shock rays to attack their opponent.
- Telepathy: Yapool as Alien Simon can communicate with someone else via telepathy.
|Ultraman Ace Kaiju|
|Verokron | Yapool | Chameleking | Vakishim | Garan | Aribunta | Giron Man | Brocken | Alien Metron Jr. | Doragory | Muruchi II | Gammas | Zaigon | Alien Antira | Unitang | Sabotendar | Baraba | Ace Killer | King Crab | Cattle God | Cowra | She-Devil | Hotarunga | Black Pigeon | Android Couple | King Kappa | Zemistlar | Aprasar | Aprasar Fairy | Space Mask | Black Satan | Giant Yapool | Mazaron Man | Yojo | Mazarius | Alien Orion | Sphinx | Alien Hipporito | Lunaticks | Undergroundmon | Gitagitanga | Red Jack | Baktari | Coakes | Bad Baalon | Kaiteigagan | Dreamgillas | Soundgillar | Machless | Snowgiran | Namahage | Alien Fire | Firemons | Alien Steal | Kaimanda | Shishigoran | Iceron | Woo II | Fubugirara | Onidevil | Gasgegon | Daidarahoshi | Hanzagiran | Verokron II | Yapool Woman | Univerlages | Aquarius | Alien Revole | Signalion | Geegon | Alien Simon | Jumbo King|