After completion of the mission "Freak Show" with an "Excellent" rating, the player unlocks Perry as a playable character in Showdown Mode.
Perry is always trying to recruit wayward youths, misfits, and freaks.
Preston O'Leary, the much-loved owner of O'Leary's Traveling Circus and Carnival Show, was killed shortly before Revolver's events, along with most of his performers, when the tent in which they slept caught fire outside of Tarnation. Due to a lack of manpower, lawmen were not available to investigate thoroughly. Perry was believed to be the man responsible.
Professor Perry, a recent addition to the (sic) circus, and inventor of Perry's Miracle Elixir has volunteered to organize the clean-up efforts. Perry stated, "The show must go on!"
The leader of the psychotic circus including Pig Josh, Professor Perry is a twisted man indeed. His best achievement as a mad scientist is his so-called "Miracle Elixir" that allows him to regenerate health despite being shot at by Jack Swift multiple times as well as teleport. When Swift arrived in Widow's Patch it was even more decrepit than when Red had last seen it. Once there, he found Katie O'Grady tied up under the water tower and proceeded to protect her from the gang. After the gang had been dispatched Perry showed up and began to teleport around until Jack eventually killed him when he ran out of elixir.