When does Harvey Birdman: Attorney at Law return?

Harvey Birdman, Attorney at Law is an adult animated television sitcom. The series was created by Michael Ouweleen and Erik Richter for Cartoon Network's late-night programming block, Adult Swim. The pilot first aired as a sneak peek on Cartoon Network on December 30, 2000. It ended on July 22, 2007, with a total of 39 episodes, over the course of four seasons. A spin-off, Birdgirl, premiered on April 5, 2021.
Harvey Birdman, Attorney at Law is the first Williams Street cartoon to maintain continuity through the entire series. The series uses a surrealist style of comedy, featuring characters, objects, and jokes that are briefly introduced and rarely referenced thereafter. Harvey's clients are primarily characters taken from the Hanna-Barbera cartoon series of the same era.