Colleen is a British collie and the lone female member of the heroic Road Rovers quintet. Colleen was the hidden villainess in the episode, "A Hair of the Dog That Bit You."
In the episode, The Rovers were in London fighting against a group of vicious werewolves, with Exile and Colleen showing scratches during the attack. Colleen turned heel later that evening when she transformed into a werewolf under the full moon the next night, and afterwards, the maniacal villainess attempted to attack fellow Rovers Shag and Blitz, who were unaware of Colleen's heel turn. The search for the werewolf ended with Blitz, Shag, and Hunter in Exile's room, while the reverted Colleen fretted about the commotion, which suggested that Colleen had no memory of her heel turn as well.
After the other Rovers leave, Exile believes that he is the actual werewolf when he sees scratches on his front door. During a mission, Exile flies (chained up) with Hunter, while Colleen files with Blitz. With the full moon in the night sky, Exile revealed that he was feeling hot, sweaty, and nauseous, but those were normal feelings for him. Exile was cleared, but in the other chopper, Colleen revealed her heel persona and transformed in front of Blitz. After her transformation, the evil Colleen attempted to attack Blitz before escaping and joining a pack of werewolves at Stonehenge. The rest of the Rovers fought them off, and later cured Colleen and the others with tennis balls laced with swamp water.