Bart is Bert's twin brother on Sesame Street. Although they look identical, Bart is the complete opposite of Bert in personality — he's cheerful, overbearing, and laughs a lot, a characteristic Ernie learns about when they first met. (First: Episode 0594) He is a traveling salesman by profession, whose wares include aluminum siding (Episode 1068).
Bert once left to visit his brother, inciting Ernie to call him during the night about frivolous details such as being thirsty. In 2003, Bart sent Bert a book for his birthday in Episode 4034, which Bert preferred to read quietly in observance of his special day.
Bart made a return appearance in 2017, redesigned as a modern hipster in Episode 4733 (performed by Martin P. Robinson). He appeared again in 2019 (now performed by Peter Linz), performing a rap intro with his brother Bert and cousin Bertina in the cold open for Episode 5005.