The first episode of The Backyardigans could refer to several different topics.
The first Backyardigans episode in all was Me + My Friends, an unaired live-action pilot produced by Nickelodeon Studios Florida.
The first animated Backyardigans episode was the unaired 2002 pilot, which starred Uniqua, Pablo, Tyrone and Tasha.
The first episode of The Backyardigans to air on television was Knights Are Brave And Strong. This was not the first animated episode produced, however.
The first aired episode of The Backyardigans to be produced was Pirate Treasure. This came first in production order.