Blastronaut is a hitman hitman (a hitman who performs "hits" on other hitmen) who first appears in "Hitman." Ice King hires him to take out Scorcher, whom Ice King accidentally hired to kill Finn and Jake.
After typing "Hitman Hitman" into his computer, Ice King finds an online ad for Blastronaut that reads: "Blastronaut — #1 solution for all hitman problems! $99.95! Place order." After Ice King places his order, Blastronaut locks on to Scorcher and blows a hole into the side of Ice King's mountain. Scorcher, however, easily slices open Blastronaut, revealing that he is merely a robotic suit operated by a naked goblin. The goblin then jumps off the side of the mountain as Ice King yells, "Come back, you wussy!"
Blastronaut's suit is a pastel-colored, humanoid robot whose armor is comparable to that of an American football player. His mint-green arms and partly yellow shoulderpads sport turrets, and over his forearms are purple gauntlets. A purple and pale-blue blaster acts as a left hand. His knee-high boots are purple and pink, but yellow over the kneecaps. His legs, also mint-green, are attached at the hips, on either side of his torso. His abdomen is a pale blue, and he wears a pink girdle with two thin, horizontal yellow stripes over each side of his rib cage. On his right pec, both of which are also pale blue, is a badge or emblem of some sort with two shades of pink. His helmet is a black orb with a series of two concentric blue diamonds at the center.
Blastronaut has the ability to lock on to targets very quickly by simply receiving the name of the hitman to be hit. As shown in the episode "Hitman," he blasted through the wall to Ice King's lair, so it is likely that he possesses missiles of some sort. He also has the ability to shoot violet/magenta laser beams. Despite his abilities, he was no match for Scorcher, being defeated in only seconds.
- Blastronaut seems to have bad accuracy since he was not able to hit Scorcher even in close range.
- Blastronaut could be a reference to Samus Aran from the Metroid series; the two suits are similar in appearance and operated from the inside.
- Blastronaut is actually a goblin in a suit, similar to the way Samus Aran or John-117 are both just humans in suits of powered armor.
- His name is a portmanteau of the words "blast" (a reference to his powers) and "astronaut" (a reference to his style).
- On the Ice King's computer, the image of Blastronaut shows him having a blaster on his right hand, but when he arrives, he has the blaster on his left hand.