Green Giller was an Alien Kaiju – and the only Insect – who served as the Monster of the Week in Ep.23 "Space Command - Kill Fireman", in the Fireman TV series, been the 23rd overall in the order of appearance.

_Bio and Abilities_
Green Giller was a monster design to kill Fireman and came to Earth to achieve this purpose along with three Masters, all of which failed in their mission before the Monster was released from its Blue Capsule; he rampage through a Farming Village and tried to destroy a Hydro Power Dam before he was taken down by Fireman with the help of SAF. Of all the Kaiju in Fireman, it was the sole Insect Monster in the series, and after King Zaura was the 2nd to almost succeed in Killing Fireman.

It's arsenal included pincers for hands and a large one on the tip end of its tail, also had Pincer like feet, though these serve no purpose but been such; Poison which he could unleashed via a bite or Tail Pincer; and Toxic Gas which it would release from its mouth. The Kaiju was Olive and Yellow Green, with two antenna on top of the head.

Green Giller's roar reuses Zigra's roar, which Jurasaurus also had.

_History_
A small farming community enters into panic when the Sky turns dark, even with the Sun still up, and though the phenomenon passes, it leave the Villagers perplex. Elsewhere, a group of three School Children see a strange man walking close to a River but disappears from sight.

Later Misaki arrives on the site of the Hydro Power Dam and Farming Village to investigate the strange occurrences; in the woods, a Farmer meets up with 2 Soldiers – one of them holding a blue capsule with Green Giller in it – all of men are Agents of Planet Green. The two new arrivals inform the Spy their world was destroy by a new Experimental Bomb and the survivors now travel the Universe for a new home, setting their eyes on Earth, but they'll need to kill Fireman, unknown to them they were heard by the three Children nearby.

When the Spy returns to the farm, confronts one of the kids, Masao, who he kidnaps to use to distract SAF and the Villagers who form a search party to find the missing boy; Misaki finds the boy's shoe with a radio receiver, the alien calling him by his true name and orders him to meet up to a recluse location up river, alone and he complies. When he arrives on site, the trap spring, locking his legs with a time bomb attach to it. Later, Masao is release while SAF searches for Misaki, been found by Chiba who then calls Umino and Mizushima to help him out; when they see the situation, Umino decides to stay to help Misaki out and orders the other two to leave.

Umino tries to free Misaki with a blow torch, despite the request from the latter to not risk his life, while his efforts is mocked by the Aliens via the receiver; in the end however, the Captain's resolve and perseverance prevail over the Aliens' own hubris, releasing Misaki with enough time to spare, though Misaki and Umino are left unconscious by the Explosion.

The three Alien Agents are located by Chiba and Mizushima and fight them; as they are beaten by the two SAF agents, the holder of the Capsule releases the seal, exploding and releasing the Alien Insect Kaiju Green Giller, killing all three Alien Green Agents in the process – the Beast proceeds to rampage across the Countryside, destroying the Farming Village on the way to the Hydro Power Dam, with Mizushima and Chiba trying to stop the Monster on the Marigon to no effect. Misaki in that moment wakes up as the Monster tries to destroy the Dam, and Transforms into Fireman to battle the Monster.

The Hero stomps on the Kaiju before it could destroy the Dam and proceeds to take him to task, but Green Giller takes the chance to pin him with his pincers, with its Bite and his Tail Pincer it injects Poison into the Hero, causing Fireman's arm and to leg turns green, the Beast then fires its Toxic Gas onto him, the Hero cover in Green Poison and severely weaken. Green Giller takes advantage on Fireman, beating him as his Power begins to run out. However, Marigon provides cover to the hero by shooting at the Monster; taking his chance Fireman powers up to burn the Poison out, then summons his FireBlade and cuts Green Gillers Head and Tail Pincer. Fireman finishes the rest of the Body with FireDash.

After the battle, Misaki and Umino stand to Masao and the other School Kid at the Dam cheering for Marigon as it passes by.