Faitan is a mass-produced combat robot developed by the Ministry of Science to test the performance of new robots and weapons. Until Mars was completed, it was the strongest robot created by the Japanese Ministry of Science. Several of them are used as combat training partners for Mars. 

A gang of pirates that steal old robots, reprogram them if necessary, and sell them overseas at inflated prices.

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Mad Mask highly resembles Pluto from Osamu Tezuka's Astro Boy series.

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This character usually goes by the name "Tick" (チック chikku)  in Osamu Tezuka's other works.

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This character usually goes by the name "Tock" (タック takku) in Osamu Tezuka's other works.

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HamEgg is one of the oldest villains in the Tezuka Star System.

Mrs. HamSalad is the co-owner of a robot circus and wife of HamEgg.

Mr. Powerful is the strongest performer in HamEgg's robot circus.

Dr. Flame is a scientist who has a particular interest in a specific species of aliens that travel the universe in the form of an orb of blue light.

Star Kong is a huge gorilla-shaped bodyguard robot for Dr. Flame that's around half as powerful as Jetter Mars.

Bruiser is a big, strong robot who works for Skunk.

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Skunk's last name translates to "stink" when written in Japanese hiragana. (くさい)

Skunk's underlings.

Aung No. 1 and Aung No. 2 are robot bodyguards assigned to protect and take orders from the director of the ministry of science.

Acetylene Lamp is a space garbage man.

Mrs. Tabasco is the scheming wife of Dr. Spice

Dr. Spice is the scheming husband of Mrs. Tabasco

It's unusual for a robot, but Copper is a street thief.
Copper has detachable arms and spare ones that can grow in their place.

Mason is the leader of a gang programming robots to be thieves.

Heck is a dangerous robot modified by Mason to be allowed to kill.

Kin Sankaku is a gangster who is always up to no good.

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Curado's appearance highly resembles Osamu Tezuka's character "Black Jack"

Chlorians live on sunless planets and survive by extracting other people's life energy.

Lord Goro is the leader of the Chlorian race.

Dr. Frankenstenten is a doctor who was kicked from the Ministry of Science for his unethical studies and practices.

Murray de Mooster is a bullheaded robot created by Dr. Frankenstenton.

A race of aliens which inhabit Planet Zaza

A robot originating from the 7th year of the Tenpo Era of Japan

Boon is an extortionist who can never get enough money. He's privy to many people's secrets.

Part of a pair of small-time villains who are criminals wanted for breaking into a computer company's safe. 

Part of a pair of small-time villains who are criminals wanted for breaking into a computer company's safe. 

Bogart is the owner of the Roboxing Tournament.

Wolf is a powerful roboxing robot, but his electronic brain is highly outdated.

Hiroko is the greedy sister of Dr. Tsukioka.

Dekara is the robotic boss of a drug ring.

Jarmo is an assassin from the Federal Republic of Ahmeria in South Africa.

Gulf is an assassin from the Federal Republic of Ahmeria in South Africa.

Gilra is an assassin from the Federal Republic of Ahmeria in South Africa.

A poacher out for a quick buck.

A former scientist whose glory days are in the past.

The president of the Republic of Lopras.

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Rock Holmes made a cameo appearance in the opening theme song for Jetter Mars, even though he never appeared in the main show. Instead, he appeared in the Jetter Mars manga illustrated by Ikehara Shigeto. His chapter was left out of the 2019 reprint of the Jetter Mars manga.

Bengoku is a studious classmate of Mars who puts studying before anything or anyone else.

Noah is Mars' arch enemy and brother, created by Dr. Yamanoue in an attempt to create a robot even more powerful than Mars.

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Gourdski appears in most of Osamu Tezuka's works in some way.