Professor Padraic Ratigan is a male sentient rat, and Basil of Baker Street's archenemy.
Professor Padraic Ratigan is the most feared criminal of the rodent world; his misdeeds are most notorious (Queen Moustoria recognized him in a split-second), but in spite of Basil of Baker Street's best efforts, he could never be captured and tried for his crimes.
Ratigan is, above all, extremely intelligent, cunning and cultured. Although he verbally insulted him on numerous occasions, Ratigan seems to consider Basil the single other being in the world worthy of his genius, and has nothing but contempt towards everyone else. As a result, he feels sadistic glee whenever he gets the chance to hurt one of those “lesser beings”, be it one of his henchmen or the mouse people in general. Ratigan fully embraces his persona as the “World's Greatest Criminal Mind” and is the embodiment of the card-carrying villain. However, the one thing he does not assume is his species. Ignoring the obvious, he gets in frantic rage whenever he is called a rat, even appearing to feel physical pain when it happens.
Ratigan is at least twice as big as most mice seen in the movie. He mostly walks on his hinder legs. He has light yellow eyes and a set of sharp teeth. His face appears to be bald; the hair is organized like a human being's (with hair on the top of the head, sideburns and a badly-shaven shade of beard). His body, however, is covered in grey fur. He has a long, thick, bald tail.
According to Ratigan himself, he has been antagonized by Basil since the very beginning of his criminal career; the two battling egos would try to outwit each other's plans, always without any real winner. This seems to have been going on for many years, with neither finding any peace of mind in the meantime, until the events of the movie in 1897, which, in spite of the criminal mastermind's eventual escape, overall ended with Basil finally gaining the upper hand and disbanding Ratigan's gang and lair. Among his notable past crimes are the Tower Bridge Job and the Big Ben Caper.
In the non-canon short story, Ratigan's early life and motivations are greatly elaborated upon. Shunned upon for all his life for being a rat in a mouse world, Ratigan nonetheless managed to build an acamedic career, although he could never become anything more than a low-ranking chemistry professor at Rodent Oxford. Eventually, he met Basil, then one of the pupils attending his classes, and certainly the most talented. Admirative of the young mouse's intelligence, Ratigan made Basil his lab assistant, intent on bringing him up as an intelligent mouse he could finally be friendly with. One day, Basil discovered an open drawer in his professor's desk, containing research the rat had made on nootropics, chemicals which, in high doses, could annihilate people's intelligence and make them into obedient sheep. Basil comments that he does not know to this day whether Ratigan had intentionally left the paper for him to find, hoping the one he considered his only friend would join him, or if it was indeed an accident. At any rate, Basil confronted Ratigan, who, instead of denying the facts, asked Basil if he would not like to rule with him. Basil, whose lonesome life had not stripped of ethics and goodness, instantly refused and publicly accused Ratigan, who let himself be arrested, played the part of a mere lunatic and got put in an asylum, of which he quickly escaped, an event toward which the Londonian society was utterly indiffernet. Ratigan sent a telegram to Basil, claiming that Basil had won a battle, but not the war.