They were originally a tiger, a hawk, and a fish, but Zirconia used a green orb to turn them into human forms (though Fish Eye's hands looked more dragonlike). They then became part of the Dark Moon Circus.
They were the first ones sent to look for Pegasus when the Dark Moon Circus arrived on Earth. For 21 episodes, they were searching for Pegasus, whom they knew was hiding in someone's dreams. Zirconia's pet eyeball, Zircon, would take pictures of several people with big dreams, and one of the Amazon Trio would choose one, and go after him or her, eventually revealing their true identity, pinning them to a wall, extracting their dream mirror, and looking into it for Pegasus (apparently causing excruciating pain). They never did find Pegasus, however, and would have killed them were it not for the intervention of Sailor Moon. They would send a Remless after Sailor Moon, but the Remless would always be destroyed.
Tiger's Eye always targeted younger girls he found attractive, and sent female Remless to fight Sailor Moon.
Hawk's Eye always targeted older women, and sent female Remless to fight Sailor Moon.
Fish Eye always targeted men or boys, and sent male Remless to fight Sailor Moon.Disappointed with their failures, Zirconia revealed to them the existence of their queen, Queen Nehelenia, and that they were originally a tiger, a hawk, and a fish, and that he would change them back if they did not capture Pegasus soon.Fish Eye was the first to question Zirconia's ways; she fell in love with Darien while targeting him, and was rejected for Serena. She also knew they didn't have dream mirrors (to remind Tiger's Eye of this, she pinned him to a wall and attempted a dream mirror extraction on him) like humans did. When Fish Eye discovered that Serena was Sailor Moon and that Rini was the one whose dreams Pegasus was hiding in, Zirconia thought that Serena was the holder of Pegasus (as Fish Eye was hesitant to reveal Rini to him), and sent Hawk's Eye after her. Fish Eye tried to stop him, and Tiger's Eye went after her to stop her from interfering, during which, after Hawk's Eye extracted her dream mirror, Fish Eye revealed that Serena was Sailor Moon.
However, Zirconia's true intentions were to kill them and replace them with the Amazon Quartet. Para Para sent a Remless named Mr. Magic Pierrot to eliminate the trio. After Hawk's Eye extracted Serena's dream mirror, Mr. Magic Pierrot attacked them and destroyed Serena's dream mirror. Hawk's Eye sacrificed himself to save Fish Eye from Pierrot's attack, and Tiger's Eye and Fish Eye tried to fight him, but were unable to defeat him, so they gave up the power that made them human, rebuilding Serena's dream mirror. Serena transformed into Sailor Moon and destroyed Mr. Magic Pierrot.
Tiger's Eye and Fish Eye died from losing their power and, along with Hawk's Eye, returned to a tiger, a hawk, and a fish. Pegasus, who was summoned by Sailor Mini Moon to help Sailor Moon destroy the clown, brought the trio back to life, restoring them to human forms and giving them dream mirrors. Pegasus then took them to his world of Elysion.