Colin is a Miniature Schnauzer that was purchased from the dog pound by Daisy. He was shortly going to be put down as dogs could only stay at the shelter awaiting adoption for a limited time. His life before his incarceration in the dog pound is unknown. He was named after Daisy's childhood pet cardboard box.
Colin first appears in "Battles", in which Daisy, accompanied by her best friend, Twist Morgan, visits the dog pound and adopts Colin shortly after learning that he is going to be put down. Daisy's flatmate, Tim Bisley, is initially unimpressed at Daisy's purchase, citing severe caniphobia. However, Colin later becomes a valuable and beloved member of the household.