Super Weapon R-1 (超兵器R1号 Chōheiki Āru Ichi-gō) is the twenty-sixth episode of Ultraseven. The TNT dub renamed this episode as The 8,000 Megaton Mistake.
Two Ultra Guard scientists, Doctors Segawa and Maeno create a new devastating weapon -- the anti-planet device they christen the R-1. Even in its infancy, the R-1 is said to have the power of 8,000 Hydrogen bombs. With plans to build an even more deadly R-2 device, it is decided a test of the weapons capabilities will be done on the supposedly uninhabited Planet Gyeron, a minor planet in some faraway galaxy. The test proves successful, but a giant flying creature doesn't take too kindly to its home being destroyed. Making its way to Earth, the monster attacks cities and emits radioactive ash. Ultraseven engages the beast in battle.
- Dan Moroboshi/Ultraseven (モロボシ・ダン／ウルトラセブン（声） Moroboshi Dan/Urutorasebun): Kohji Moritsugu (森次 晃嗣 Moritsugu Kōji)
- Anne Yuri (友里アンヌ Yuri Annu): Yuriko Hishimi (ひし美 ゆり子 Hishimi Yuriko)
- Shigeru Furuhashi (フルハシ・シゲル隊員 Furuhashi Shigeru): Sandayū Dokumamushi (毒蝮 三太夫 Dokumamushi Sandayū)
- Kaoru Kiriyama (キリヤマ・カオル Kiriyama Kaoru): Shoji Nakayama (中山昭二 Nakayama Shōji)
- Soga (ソガ Soga): Shinsuke Achiha (阿知波信介 Achiha Shinuske)
- Amagi (アマギ Amagi): Bin Furuya (古谷敏 Furuya Bin)
- Narrator (ナレーター Narētā): Hikaru Urano (浦野光 Urano Hikaru)
- Ultraseven (ウルトラセブン Urutorasebun): Koji Uenishi (上西弘次 Hirotsugu Uenishi)
- Ultraseven Volume 7 Features Episodes 26-29.
- As of March 2011, this episode has been banned from television in Japan due to the Fukushima Daiichi nuclear disaster. This is due to a scene where Gyeron wipes out a power plant with a giant wave after he lands in the sea. This makes Gyeron the second of two characters from Ultraseven to be banned from reappearing, with the other one being Alien Spell. However, Gyeron still appears in stage shows, unlike Spell, who only appeared in their debut episode. The episode is also readily available online, and appears to still be popular among both American and Japanese viewers.
- This episode is a satire on the Nuclear Defense Strategy during the Cold War.
- The figurative statement quoted by Dan, "a lonely marathon you continue spitting out blood", was later used in Heisei Ultraseven 1999 episode, "Legend and Glory", to cite TDF's ongoing implementation of Friendship Plan agression plot following Furuhashi's demise at the hands of Alien Valkyrie.