The original premise of this series was the monsters are created by "Minus Energy" as result of negative emotions of humans, after three episodes this premise seems to be all but forgotten as the space monsters and alliens start appearing. Ocassionally the writers will make a brief return the idea of "Minus Energy" monsters. "Minus Energy" monsters appear in episodes 1, 2, 3, 36 and 49.
Episode 4: Zandrias - first space monsters in this series, there were two of them mother and son, the son was angry at mother and hid on Earth, she came to take him home but he wont go, so Ultraman 80 attacks the mother to awaken the son's love for his mother, it works, almost too well, he has to play dead to get them to leave
Episode 5: Alien Bam (first aliens in this series) and their giant robot Mechagiras, the aliens who know he is Ultraman 80 trap Yamato, Takeshi in "Fourth Dimensional Space" where he cannot transform, and send Mechagiras to attack Tokyo
Episode 7: Noiseler - space monster, destroys noisey things like super sonic aircraft and high speed passanger trains, it actually liked the music played by 4 teenage boys from Yamato, Takeshi's class and danced to it, if UGM hadn't fire on it it may not have become aggressive again, first monster not killed as Ultraman 80 lead it back into space instead
Episode 10: Alma - alien, childhood friend of Ultraman 80's, preteneds to be Yamato, Takeshi's wife
Episode 11: Medan - tiny monster hatches from an egg, destroyed but some cells survived inside a sea shell which was taken into UGM base, where they grew into a new monster, which attacked UGM support personnel and passed through UGM natural gas pipes into the city's natural gas pipe lines, this monster is so full of natural gas UGM cannot fire on it out of fear it explode and take the pipelines wiith it, and to make matters worse a thunder storm rolls in and a lightning strike could have the same effect (first episode in which Yamato, Takeshi is seen only as UGM officer not as a school teacher though he does mention having a class the tomorrow)
Episode 12: Alien Vibros & Gora - the girls in Yamato, Takeshi's class attempt to pull a trick on "Professor" (glasses wearing litttle boy) by leaving him a fake "secret admirer" letter but then he actually meets a girl named Milly, where the letter signed "M" told him to meet the girl, unfortunantly for "Professor" the girl Aoyama, Milly is not actually the daughter of an American man and a Japenese woman, who has been living in the Netherlands and so doesn't know Japan very well, as she tells Yamato, Takeshi but is actually an Alien Vibros who has made several attempts on the life of Yamato, Takeshi and ultimately releases the monster Gora to kill Ultraman 80, so her kind can conquer the Earth to use it as a base for further conquest of the universe, despite actually developing feelings for Hiroshi aka "Professor" (Yamato, Takeshi lies to Hiroshi, telling him Milly went back to the Netherlands when in fact she went back to her world, probably to be executed for failing to conquer the Earth, this is the last episode featuring the school or the students)
Episode 13: Alien Gorgon & Saramandora - Alien Gorgon send Saramandora to attack Japan, while their agents assassinate the UGM Europe and UGM North American captains, when the assassin sent after Japan's Captain Oyama, Kazuki is killed by the captain its body turns into that of a woman and he is accused of murder, the aliens digused as humans lead protests against UGM , then they send a second version of the monster when they are exposed for what they really are (Saramandora reappears in Ultraman Mebius episode 17)
Episode 15: Mue - a tiny, passive, alien creature brought to Earth by a member of the Space Mammy crew, a mad scientist aubducted it, experimented on it (torturing it). transforming it into a human sized creature and then into an agressive giant monster, which stepped on the scientist crushing him to death, Ultraman 80 shrinks Mue back to its original size and carries it back into space where it belongs
Episodes 17 & 18: Lavras - UGM Chief Ito, Junkichi was transformed into this monster (the woman he's looking at is his girlfriend, a friendly alien in disguise), initially passive Lavras does not become aggressive until a strange roaring coming from a cave drives Lavras and the sea monster Daron mad, Ultraman 80 is at a disadvantage as he knows this monster is a human turned into a monster against his will
Episode 19: Gaus - only survivor of a planet blown up by Earth, a red star was on a collison course with Earth so Space Mammy wes sent to delive almost all of Earth's nuclear weapons to blow it up, Yamato, Takeshi, knew that one of the planets orbiting the star, Gaus, was inhabited but he couldn't figure out how to tell the humans without revealing how he knows, that he is Ultraman 80, as Ultraman 80 he lets the attacking monster surrender and teleports to a new planet since it was after all just responding to the destruction of its home planet (not the first time the humans in an Ultraman series destroyed an inhabited world and the last survivor came seaking revenge)
Episode 21: Alien L85 Zuckal - Zuckal is a Space G-Man, monster hunter from Andromeda galaxy, came to Earth seaking the monster which had killed his wife and children 20 years ago, when photographed at a scene of wanten destruction Yamato, Takeshi is so offended that an alien species he knows,is peacful would be blamed that blurts out that inhabitents of L85 are peacful and wouldn't do such a thing, of course he cannot explain how he would no such a thing (oosp), Zuckal giantsizes and tries to take down the monster alone
Episode 22: Queen Einus & Underground Men - another underground race (4 billions strong), this group wants to blot out the sun
Episode 23: Amehza - spance tanker. "Space 7" exploring the Amoeza Nebula is contaminated with space amoebas, when "Spacy Mammy" comes across the ship Yamato, Takeshi enters it to pilot it away from Earth, on an asteroid the space amoebas merge to form the giant monster Amehza
Episode 25: Argon - two UFO's appear over UGM headquarters in Japan, one is shot down by UGM, a female UGM trainee Jun, gets to the saucer before UGM officers and finding what appears to be a man, though she knows its an alien in disguise, who pretends to be friendly, instead of waiting for actual UGM officers to show up she takes him away so she can present him to UGM later in order to show up the only female UGM officer Jono, Emi, the alien eventual shows its true colors by transforming into the giant Argon to attack the UGM base, Jun than steals a UNDA jet to attack the monster (I think Jun should have been rejected as a UGM candidate and sent back home ifor showing such poor judgement and reckless behaivor instead of saying "when you are young you are allowed mistakes" and sent back to continue her training)
Episode 27: Alien Argo - homless wander after its planet fell into a black hole, came to Earth to eat humans, actually existed without physical form, appearing as a white foam and shadow, untl it took possession of a human scientist insteas of eating him, which resulted in ita demise as Ultraman 80 killed the giant it turned the man into, [third time Yamato, Takeshi and Jono, Emi are partnered] (this episode introduces two new UGM member Fujimori, Shinpachiro and Ikeda, Noboru)
Episode 28: Bal - (friendly baby monster bird) & Zakira (monster which eats Bals, killed the baby's parent now whats to eat the baby)
Episode 30: Alien Zatan & Zatan Silver - two of these alians disguised themsevles as humans, a reporter friend of UNDA Public Relations officer Sera, Teruo, and the reporter's camera man, after they were discovered they summoned the giant robotic monster Zatan Silver
Episode 32: Barrack Ship - some mysterious force is sinking ships at sea, at first the waters near Japan seem safe but of course that doesn't last, the mysterious force turns out to be an experimental computer controlled, unmmaned cargo ship which after striking an iceberg and sinking 15 years ago has redsurfaced and is attacking other to use them to build itself into an iceberg prove ship so it can carry out its last programming and return to Tokyo bay (Barrack Ship is similar to Iron Rocks from Ultra Seven episode 21, except that ship was controlled by aliens)
Episode 34: Angoras - a new type of fish caught of the coast of Japan turns out to be the baby of a giant fish (not really a monster, just a huge fish) and it wants its baby returned, when the baby is released mother and child return to the depths of the sea
Episode 35: Fire-Draco - 300 years ago a 3 head dragon was defeated, its 3 heads cut off, those three heads repear in the form of two circus performers, a fire breather dressed in red, a strong man dressed in blue and a young orphan boy dressed in white (since Yamato, Takeshi can communicate with the boy telepathically they must actually be aliens), when they boy who is tasked with polishing the "Dragon Gem" he actually steals it and when all three touch the gem they vanish and Fire-Draco appears, the monster is actually over powering Ultraman 80 until the white head rebels and bites the red head's neck
Episode 38: Ghostdon - two men die in a truck crash, the driver lives long enough to tell his son a monster caused the crash but no one believes the boy until the monster strikes again (this episode is as annoying as Ultraman Leo episode 46 which it copies, monster after monster appears on the Earth yet know one belives a monster forced a truck off the road), Ghostdon is actually an evil spirit seaking a physical form, when two boy indulge in a kite fight (a discusting concept teaching young boys exactly the wrong things) with one kite painted with Ultraman 80 on it and the other with a monster painted on it, Ghostdon picks the monster on the kite for its form, lightning from this monster causes Sky Higer piloted by Yamato, Takeshi to crash, he parchutes out but the monster hits him with a bolt, on the ground Yamato, Takeshi tires but failes to transform, for the first time he's afraid he's going to die, then he hears the voice of the Father of Ultra speaking to him from the Land of Light and spured on by his commanding officer's command to "rise and fight as a bolt of justice against evil" he does so
Episode 40: Sumo Boy & Jihibikiran - a spirit that appears as an unnaturally strong,young boy who likes to sumo wrestle, until gets angry then he becomes a giant, tricked by two thieves to attempt to climb an electric fence the shock makes it angry, Jihibikiran isn't evil it just wants to wrestle so Ultraman 80 challanges Jihibikiran to a match, after which it reverts back to Sumo Boy form and returns to sleep in the mountains for 20 years
Episode 42: Zurasuimar - a monster sleeping under a statue, awoken when the statue blown off its base by two theives who think there is 2 billion yen hidden under it (there isn't)
Episode 44: Delusion Ultraseven - after being ran over by a street thug on a dirt bike a young boy ends up in the hospital where he dreams of his hero Ultra Seven appearing to save him, in the real world the boy's spirit enters his Ultra Seven doll which giant sizes and hunts down the motorycle gang forcing a battle between Ultraman 80 and what appears to be his kin Ultra Seven [this should have been a "Minus Energy monster"]
Episode 46: Marjin & Red King III - Marjin is a genie who lives in a jar, he grants wishes (toys and games), exhausted after granting many wishes he misunderstands a wish for "Red King just like the real one" and instead of conjuring a toy Red King he summons the actual giant monster (Red King originally from Ultraman episodes 8 & 25)
Episode 47: Glovusk - a disgarded baseball glove is turned into a giant monster by ultraviolet rays (once again this should have been a "Minus Energy" monster, created by a child's anger and disappointment but wasn't) [the "science" in this episode is totally wrong, ozone is actually created by ultraviolet rays and it absorbs infrared rays, not ultraviolet, as long as the sun exists there will be ultraviolet rays producing ozone, pollution is not destroying the ozone layer, on the contarary it is increasing ozone layers at the surface of the Earth, and that is a problem as too much ozone is toxic]
Episode 49: Plazma & Minazma - brother monsters which nearly defeat Ultraman 80 (because Yamato, Takeshi was wounded by Minazma before he could transform) , untilf Princess Yullian comess to his aid, the last two monsters actually fought by Ultraman 80