Eventually, he was hired by Warner Bros. Animation after replying to an ad for storyboard artists in The Comics Journal placed by animator Bruce Timm, with Cooke shocked that there were positions available. His successful pitch included 14 pages that eventually would be published in 2000 as Batman: Ego. Originally freelancing from Toronto, Cooke met his animation colleagues at San Diego Comic-Con and was approached about moving to Los Angeles full-time. Despite no desire to live in Los Angeles, Cooke moved there to take advantage of "an opportunity to be a part of something that was never going to come around again this way," the ability to associate with creators such as Bruce Timm, Paul Dini, Alan Burnett, and Eric Radomski. Cooke worked as a storyboard artist for four episodes of The New Batman Adventures as well as a handful of episodes of Superman: The Animated Series. In 1999, he designed and animated the opening sequence for Batman Beyond. In contrast to most cartoon openings—which adapt music to a finalized group of shots—Batman Beyond's visuals were specifically cut to suit the music, after Cooke's successful pitch of the concept to Bruce Timm. Surprisingly, Cooke employed his personal Macintosh computer in his spare bedroom and Adobe After Effects for most of the animation, as opposed to Warner Bros.' resources. According to Cooke, the Batman Beyond team created a strong show in light of what he considered "kind of a disheartening mandate from the network," which wanted a show about the Batman of the future. He believed the WB Network ultimately disliked the show's level of violence and prematurely ended the show once it could be syndicated. Cooke then worked as a director for Sony Animation's Men in Black: The Series for a year. In April 2014, Cooke released a Batman Beyond animated short celebrating the 75th anniversary of Batman. Justice League: The New Frontier In July 2006, it was announced that Warner Bros. Animation and DC Comics would release a series of direct-to-DVD DC Universe Animated Original Movies based on important DC comic books. Due to the adamance of DC's then-Senior Vice-president of Creative Affairs Gregory Noveck, the second film to be adapted was Cooke's DC: The New Frontier, produced by Bruce Timm. Due to Cooke's obligations on The Spirit, Stan Berkowitz wrote the film, while Cooke storyboarded ten percent of the film, rewrote and polished dialogue, as well as provided