Professor Clover

Professor Clover (known as Agent Clover in the past) is one of the main antagonists of the Kaitou Joker series.

History
Not much is known about his past, except that he went to the Pandora Kingdom to get the Pandora key so the Federation could achieve its goal.

Clover failed to get the key, though. Due to Joker, Queen, Spade, and young Silver Heart (known as Agent Silver Heart at the time) stopped him. During a fight with the three phantom thieves and one agent, Clover got his arm shot off and almost died. He was, however, saved by his present day self.

Sometime before the series, (when Clover was called Professor Clover) he alongside Doubt disguised himself as Joker's deceased parents in order to steal the Time Telling Goddess statue that was in Joker's mansion.Joker saw through his and Doubt's disguises, though. When he noticed that his parents were acting strange. (they didn't know who made the curry, and kept on insisting that Joker tell them were the key to the safe that the statue was in, something Joker's parents would have known) and was defeated when Silver Heart used a wire coil that was around the safe as an electro magnet.

Around the time Clover met Joker, he also met Diamond Queen (known as Queen Emerald at the time, the event happened in the anime only) and Shadow Joker (possibly known as Cyan at the time, the event might be in the anime only) In the anime, he met Queen when she was visiting her parent's grave, and lied to her that Silver Heart was the one who killed her parents. He then let her stay with him with the promise that she would be able to get her revenge on the phantom thieves. In the manga, he did not meet Queen in her past, and Queen found out about what happened to her parents when looking through some old papers.

It is unknown when Clover met Cyan, but Shadow ended up staying with him when a promise was made: He'd get the three magical crystals of the staff of Kairos, and Shadow's sister, Rose would wake up.