A supporting character from the 1983-1985 cartoon-series "He-Man and the Masters of the Universe" by Filmation and also a featured character of the "Masters of the Universe" (MOTU for short) toy-line by Mattel.

In the cartoon Duncan is an inventor, soldier and foster-father of Teela (who is the daughter of Zoar, the Sorceress of Castle Grayskull). He bears an armour which is slightly different from that of the standard uniform of the royal guards and a moustache (which the original action-figure lacked). He has an understanding fatherly voice and rarely loses his temper (except maybe if Orko's around). Duncan was a regular during the show's three-year run since he is one of the three people who know He-Man's secret identity (as explained in the intro-sequence of the cartoon).

He is often depicted as a bit of a joker, particularly in the 1987 movie-adaption of MOTU which also potrayed him as an unorthodox soldier. This causes a brief argument with Teela in one of the scenes of the movie.

The 2002 cartoon portrayed Duncan as a much more masculine, serious and perhaps a bit darker character.