Doug Shablowski

Doug "The Doppelganger" Shblowski(?) is an otter that made his first appearance in the episode Temp Check as the main antagonist. He is an otter that just came to Mordecai and Rigby's town. He began working as a temp for Rigby, but then started to copy Rigby's actions, appearance, and voice, later in the episode he actually became Rigby, and was very hard to tell apart from the actual Rigby. In the climax of the episode, Doug was chosen over Rigby as the "real" Rigby. He is later found out by Mordecai, and arrested. He apparently had been pulling this scam across the country. He was taken to prison.

Appearance
Doug is a brown otter with black, long whiskers and a pronounced, black nose. When he first arrived into Mordecai and Rigby's city, he was wearing a white, long-sleeved shirt, blue jeans with a belt, and an orange and white trucker hat.

Abilities
Doug, as his name implies, is able to copy anyone's voice, appearance, and general abilities. He began taking Rigby's form when Mordecai and him were trying to make an impression of him. He would later copy Rigby's hairstyle and gain the black circles around his eyes. Doug then finished his transformation by becoming an exact copy of Rigby.

Doug also seems to be able to take the person's memories, or at least learn them incredibly fast. During a trivia test about Rigby, he was able to correctly answer questions about the person he copied.