With Richard Linklater's “Boyhood” hitting theaters, the director has started casting another passion project — WB's remake of “The Incredible Mr. Limpet,” which has Jon Hamm circling a live-action role opposite Zach Galifianakis, and comedy stars Danny McBride, Sarah Silverman, Kevin Hart, Josh Gad, Keegan Michael Key and Jordan Peele in talks for various roles, TheWrap reveals citing multiple individuals familiar with the fantasy adventure movie.

Warner Bros. had no comment.

Linklater will direct from a script based on the novel by Theodore Pratt, though the project has had a prolonged development period, as WB has been trying to update the story for two decades. The original 1964 adaptation of “Mr. Limpet” was directed by Arthur Lubin and starred Don Knotts as the title character.

Bill Gerber (“Grudge Match”) is producing the modern-day update under his Gerber Pictures banner along with Akiva Goldsman of Weed Road.

Production could start as soon as this fall, provided talent deals close and the cast's availability works with Linklater's schedule, though the live-action scenes may not be filmed until early 2015.

Linklater has already recruited his “Waking Life” and “A Scanner Darkly” collaborators, Femke Wolting and Tommy Pallotta, to test rotoscoped animation concepts.

Galifianakis is expected to star as Larry Limpet, a bearded beach bum trying to save the fish population. When he's turned into a fish, Limpet sets out on an adventure to save his town and the sea world, learning valuable lessons along the way.

Hamm is being courted to play the human villain, a shrewd businessman who mines the ocean floor, while McBride and Silverman are in talks for live-action roles. Hart, Key and Peele are expected to voice sea creatures in the movie.

Asked last month whether he and Peele were going to be involved with “Mr. Limpet,” Key told TheWrap “that's the plan, as it stands.” The comedic duo are currently filming the fourth season of Comedy Central's hit series “Key & Peele.”

Best known for his iconic role as Don Draper on AMC's “Mad Men,” Hamm recently starred in Disney's “Million Dollar Arm.”