Walter Sebastian "Embarrassing Dad" Duncan is Jeremy's father. Born approximately in 1954, an orthodontist who, like Connie, finds it almost impossible to hold a conversation with his son. Walt is portrayed as clueless and old-fashioned about technology, especially computers and video players. Despite Jeremy's attempts to explain how to use devices, Walt is unable to comprehend even the most basic functions. Walt is shown as having problems with math, as all he knows is the Pythagorean theorem. He has been shown to think that a fan belt is part of a search engine and that "Googling" somebody means having sexual intercourse with them. His interactions with Jeremy's peers cause intense embarrassment for his son, as Walt makes comments such as "What's up, dood?", not knowing the meaning behind them. He is the designated clothes launderer, often getting into arguments with Jeremy over notes in pockets, socks inside-out, and other pet peeves. Walt constantly wears oversized blue pants, plain white T-shirt, black vest, and a combover, which makes him look like a Walmart employee. Walt occasionally reveals memories that attest to a wilder youth, but most of these anecdotes are nonsense. According to Connie, his army jacket which "holds awful memories" was picked up by Walt at a thrift shop on a day when "the traffic was terrible", and when dating Connie, he once gave her a bong, mistaking it for a flower pot. In one instance, Walt recalls how uninhibited he felt one night at a Moby Grape concert. This shocking recollection causes him to forbid Jeremy from attending a similar concert. Another time, Walt reveals he has had a peace sign tattooed on his rear end since the late 1960s, which has expanded along with his rear end, and is described to now be the size of a stop sign.
However, at times, he has been as cool as he can be to his son, like when he got a Guitar pick from one of Jeremy's favorite bands who turned out to also be orthodontists.