Duncan and Harold started off not liking each other right away, when the punk threatened the nerd with his fist to not smile at him before the teams were even set up. This escalated to Duncan pranking Harold, such as putting his hand in warm water when he was asleep.
Despite Harold's benefits to the teams, Duncan did not let up. Leaving him naked for the girls and the viewing world to see was Duncan's idea for fitting punishment over Harold's messiness. Geoff assisted Duncan in pranking Harold endlessly throughout challenges, until they eventually lost and decided to vote him off. But Harold had had enough, and to get revenge on Duncan, he rigged the votes to have Courtney, who the punk had fallen for, eliminated.
After the season, Harold felt guilty about what he had done to Courtney, but still had not forgiven Duncan.
As the contest started up in TDC, Courtney was determined to have revenge on Harold for her unfair elimination. She asked Duncan to help her, and he was all to glad to assist in getting back at the nerd. The punk was quite passive about how aggressive his girlfriend had become, and was pretty much okay with how much Harold and others were hurt on sudden eliminations.
When Courtney spiked the food in an eating challenge with Gummi Slugs, Duncan pretty much figured out it was her but refused to tell anyone. He had been unable to get through to her for some time, and blamed Harold for being the one causing her ire. Eventually, Duncan was voted off for helping Courtney, and suffered some payback at Leshawna's hands.
In the second challenge, Car Race, Duncan and Harold were shown to still be feuding over what happened in the past two seasons. While Harold had forgiven Courtney, he still held Duncan accountable for much of what happened, and had expected the punk to apologize at some point; this was not in Duncan's character, and he decided to just let the feud continue.
Duncan was eliminated in Car Race, which infuriated him a great deal, especially since the final two of possible eliminations was Harold himself. After throwing a short fit, he took control of the Bus of Losers. He has continued to come back to the stadium, but has left Harold alone for the most part, interacting with Courtney and Gwen instead.
- In Total Drama Island, this was the second most heated feud of the show, right behind Gwen and Heather.
- Despite their heated rivalry, which normally leads to yaoi stories by fans, there is very little of this in the fan community. (Duncan is usually paired with other boys.)
- While they are not friends, Harold was cheering for Duncan in his boxing challenge with Colin, because Colin is far worse than Duncan in every way.