Pat was born in 1938 and his most distinguishing features were his spiky grey hair, shredded wheat coloured moustache, sideburns and gold jewellery.
He was a milkman working for the Craggy Island Creamery. Pat was a sleazy, sex crazed maniac who slept with the women he delivered the milk to every morning.
He also had several bumper stickers on his milk float such as "Young Banger" and "Milkmen Do It On Your Doorstep".
Pat Mustard delivered milk to the parochial house and was Mrs. Doyle's love interest, who even volunteered to look after Pat's giant wrench.
Pat told her several fibs about being a swimming instructor, a soldier in Vietnam, a former Mr. Universe and teaching Elvis Presley how to play karate.
Mrs. Doyle said she was low on milk and kept on using lots in Ted's tea so Pat Mustard would come more often.
After Ted looked at some photographs of babies that he and Dougal had judged during a baby competition, they noticed that their hairiness bore a striking resemblance to Pat.
Ted confronted Pat about this, but the milkman told him that he would have to get up very early in the morning to catch him. Ted did just that and after showing some photos of Pat's behavior to his boss Mr. Fox, Pat was sacked and Dougal took his place.
To exact revenge, Pat Mustard placed a bomb on the milk float and phoned Ted telling him that when Dougal drove over 4 miles an hour, the bomb would be armed, but would go off if he went under 4 miles an hour and kill him.
Ted in his panic forgot to hang up the phone, leaving Pat still calling him from a phone booth. After Ted safely removed Dougal from the milk float with help of a brick, it continued on its way into the direction of where Pat was still in the phone booth, laughing evilly. After the milk float crashed into the phone booth, the bomb went off and killed Pat with the sound of the explosion echoing all the way to the North Pole.
After Pat's death, a heartbroken Mrs. Doyle goes over to her mantle piece in the kitchen that has several pictures of Pat, candles in milk bottles and his giant wrench hanging on the wall. She sadly takes it all down and puts them in a box, presumably to bury them.
Later when Ted is putting out the garbage, the brick that saved Dougal comes down from the sky and hits him with one of Pat's bumper stickers, that says "Shit Happens".
- Despite sleeping with every woman on Craggy Island, he did not sleep with Mrs. Doyle.