- For the horse, see Duncan.
| Character Information
Duncan is an auctioneer at Gavelby's Auction House.
When the Simpsons bought a painting from the Van Houtens, they took it to Gavelby's Auction House to get appraised by Duncan. He told the family it was a genuine Johan Oldenveldt painting and expected it to go between $80–100,000. Later, Duncan was auctioning it off when Dawn entered the auction house to claim it as it was her painting. Duncan then gave Dawn a ride home.
Duncan was auctioning off the painting The Poetess at Gavelby's Auction House, which Homer wanted. After it was bought by Megan Matheson, the painting got stolen on the way to Megan's house, so Duncan called in the help of Manacek to find who stole it. Duncan told Manacek that he was the best freelance insurance investigator in the business. After Manacek figured out who stole the painting, Duncan was there for the unveiling of the thief. Duncan was surprised that the painting was stolen because the painting was secure in the vault of the auction house.