Cap'n LardButt, known as just LardButt for short, is a pirate who the seas and resides in the sewers. His debut blooper is "SM64 Bloopers: The Pirate Plumbers".
He has a red cap and a red shirt, as well as white overalls. He also has an eyepatch, red overall buttons, a Jolly Roger on his cap, and a thinner and curlier moustache.
Much of the time, Lardbutt appears to be a stereotypical pirate, using a heavy accent and similar clothing. While much of his personality is not shown, he appears to be devoted into capturing the Squid Monster (revealed to be Ben's squid pet mutated). It was shown that Lardbutt greatly likes his sandwich, and will lash out at anyone who interrupts him or messes up with his sandwich, such as how Mario and Ben, who were fighting, accidentally bumped on Lardbutt, making him drop his sandwich on the ocean. Acknowledging that Lardbutt was angered, Mario quickly blames Ben, which makes Lardbutt chase Ben around the pirate ship's deck, infuriated.
His first appearance so far is in "SM64 Bloopers: The Pirate Plumbers". He later reappears in "Mario Simulator Interactive! (500k Subscribers)". In this video, he is shown to have a crew consisting of Foxy the Pirate Fox and a Shy Guy whereas he doesn't have any crew members in the former save for Mario, Luigi and Ben.