Phineas T. Barnswallow is the comic villain of the first Sesame Street Live tour, A Sesame Street Mystery: The Case of the Missing Rara Avis. Modeled after W. C. Fields, Barnswallow is a flowery-talking showman and con artist, proprietor of Barnswallow's Barnstorming Aviary. Barnswallow hopes to take his troupe, The Seedy Birds, to Broadway, but requires a star performer. Big Bird comes across his path, and is roped into the act.

Veteran Broadway performer Grenoldo Frazier recorded Barnswallow's voice, and also performed him in-suit. The characters name is a nod to Phineas T. Barnum, better known as P.T. Barnum, one of the men responsible for the Ringling Bros. and Barnum & Bailey Circus.