The Tough Gillaco(s) (タフギラコ Tafu Girako) were a pair of infant monsters that first appeared in episode 5 of The☆Ultraman.
Subtitle: Underground Child Monsters (地底子怪獣 Chitei Ko Kaijū)
The Tough Gillaco siblings hatched shortly after their parents ravaged landscapes from beneath Africa and Japan, consuming whatever vegetation was available. The baby reptiles scurried their way to the surface and soon found their father, Tough Gillas, feeding on some of the local vegetation. During the Scientific Defense Guard's assault on the monsters, their mother, Tough Gillan, came to protect the Tough Gillacos. Oblivious to what was going on, the Tough Gillacos continued eating while their parents attacked the Scientific Defense Guard and later Ultraman Joneus. However, once Joneus killed their parents, the Tough Gillaco siblings attacked by fruitlessly gnawing on the hero's legs. Not wanting to kill the newborns, Joneus shrunk the Tough Gillacos to the size of house cats before flying off. Not wanting them to be abandoned, Professor Henry Nishiki took the Tough Gillacos and adopted them as his pets.
- Height: 8 m
- Weight: Unknown
- Powers and Weapons
|Pigu | Seagra | Spiral | Wanigodon | Red Smogy | Tough Gillan | Tough Gillas | Tough Gillaco | Fire Badon | Combugon | Robot No.101 | Alien Baltan | Mikonos | Dolfiego | Xalome | Hectore | Liquid Monster | Opt | Garadoras | Xyclon | Gellon | Gadon | Goglan | King Moa | Badan | Islanda | Spirit Parasite | Gerada | Janyur | Bedoran | Bader Group | Bagon | Janyur III | Zaanmoth | Zanba | Dragodos | Death Balan | Gibaaroga | Red King | Aboras | Banila | Arstron | Ghostron | Gokinezula | Alien Baladon | Dabaran | Alien Jadan | Jagon | Skeldon | Garbados | Megasaura | Alien Babilar | Gamiba | Inbedian | Goadarion | Jinario | Groteng | Plazoon | Agujon | Deathpower | Zuma | Gurol | Putgolia | Iddunus | Darantulas | Noa | Hellar | Roygar | Panther | Hellar's Soldiers | Gumons | Hell Cat | Orolan | Gilos | Alien Gilo | Imitation Ultraman Joneus | Hatari | Dostony | Spader | Caperadon | Alien Scien | Golding | Gedon | Hella Umaya | Makdatar|