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 Character traits
 Physical traits
He is an athletic and smooth-talking corporate personality who wears blue and red tights, a red cape, white gloves, and the Duff logo emblazoned across his chest. The ensemble features a red hat, dark sunglasses, and a "utility belt" of beer cans around his waist.
 Other traits
Duffman is generally known for his overly enthusiastic speech in which he refers to himself in the third person, complete with dramatic pauses and ending with a suggestive "Oh, yeah!" and pelvic thrusts. Fittingly, his theme song which plays at every corporate-sponsored appearance is "Oh Yeah" by Swiss band Yello. Also, Lenny calls him "the guy who creates an awareness of Duff".
When Lenny mentioned that he had heard Duffman died of liver failure, Duffman scoffed "Duffman can never die! (Pause) Only the actors who play him!" This is a reference to real-life corporate mascots such as Ronald McDonald and the Marlboro Man who have been portrayed by multiple actors. The connection to Marlboro Man is expanded by the fact that two of the actors who played Marlboro Man died of lung cancer, a disease related to the product they promoted. Duffman was also shot by Frank Grimes Jr., and although the wound was not necessarily fatal, Duffman pledged his love to Doris before blacking out. Another Duffman was possibly killed in a blimp crash during a baseball game; it was then revealed that there were three Duffmen working the game that night. The Duff corporation does not publicly acknowledge that Duffman is only a fictional character, so as not to disillusion Duffman's "fans". Actors to portray him have been named Joe Duffman, Sid, Larry, and twice, Barry Duffman.
 Life outside business
Though he is a corporate puppet of Duff Beer, some actors have displayed independent thought and conscience at times. Homer discovers that Howard K. Duff VIII, who owns not only the beer company but also the Springfield Isotopes, was planning to move the team to Albuquerque. Commanded to help discredit Homer, this Duffman was torn between corporate loyalty and the truth. In the end, Duffman said to himself "New feelings brewing in Duffman! What would Jesus do?" and tossed Howard Duff into the stands of Isotope Stadium.
Homer and Marge attended an Oktoberfest celebration, where Duffman energetically proclaims "This Reich will last a thousand beers! Oh, Ja!" -a reference to the Nazi concept of a Thousand Year Reich. Under his breath, he mutters "I do this, and I'm Jewish".
Duffman claims to have two children, Dufflad and Duffgirl, but Mr. Duff VII retorts that these were "one-time shots in a Super Bowl commercial". This Duffman was named "Sid". Also, Duffman said "Are You there, God? It's me, Duffman!". Duffman (or at least this particular Duffman) also mentioned after distributing several Duff memorabilia that he has to leave early to comfort his daughter who dropped out of College.
Duffman (or rather, whichever actor was playing him at the time) was revealed to be bisexual.
Duffman also slept with Titania. He promised her that in exchange for sleeping with him, she wouldn't have to touch the drunks in a bartending contest, but he reneged on the promise at the last minute.