Fat Blue, Gus
They first appeared in Episode 2643 as delivery men for Gus' Letter and Number Store. Although they arrive late with Big Bird's letter deliveries (due to the Martian Day Parade in town), they manage to deliver his numbers on time and are rewarded for their efforts with a poem about them. They appeared again in Episode 2646 to extract Preston Rabbit's Illustration-Activation machine. In these appearances, Rick Lyon performed Gus and David Rudman performed Tyrone.
The pair later appeared in a Monsterpiece Theater sketch, "The Postman Always Rings Twice", where they arrive at Grover's house to deliver a table (signaling their arrival with four rings of the doorbell). They also made an appearance in a Waiter Grover sketch, moving a table out of Mr. Johnson's reach. In these sketches, Rudman continues to play Tyrone, while Kevin Clash takes over as Gus.