Merriwether von Weasel is a one-shot guest character seen in the third season story "It's a Bird, It's a Plane...It's an Elephant?" Merriwether is an expert navigator and pilot, but in this story, his balloon gets stuck in a tree. In the story, Peanut states that he previously met Merriwether when he got lost on the way to the Lake Doohickey Hot-Air Balloon Party, though this was never shown on the program itself. Merriwether wears a monocle and a pilot's goggles. In return for the help of PB&J and their friends, he gives them a ride on his hot-air balloon, which features an elephant design. He speaks with a bit of an accent, possibly British.
He joins the kids in a Noodle Dance to brainstorm a way to get his balloon out of a tree, and seems very much into it.