He also appeared in DinerTown Detective Agency as one of the possible suspects and informants of various cases. It is implied that Leo the Lovebird is his brother as Kingston referred him as Uncle Leo.
In Parking Dash, Duncan (or someone who looks identical to him) appears with a different appearance. He is given a personality similar to the Lovebirds in which he is deeply in love, so much in fact that he can't remember what his car looked like after giving it to Karma.
Duncan appears as part of the crew in Soap Opera Dash as the stage cleaner.