After graduating in 1991, Darnell joined Pacific Data Images,[2] where he worked as a character animator on the 1991 Hanna-BarberaHalloween special The Last Halloween. He also animated and directed the short film Gas Planet, which won the Ottawa International Animation Festival Special Jury Prize.[2] In 1995, he left PDI to join DreamWorks Animation, where he helped with research and development for The Prince of Egypt.[2] Shortly after DreamWorks merged with PDI the following year, he was assigned to direct his first feature film, Antz, co-directing alongside fellow PDI-turned-DreamWorks employee Tim Johnson.[2] The film, released in 1998, marked the studio's first computer-animated feature film, and the second computer-animated feature film after Pixar's Toy Story.[2] He then worked as a storyboard artist on the 2001 film Shrek, for which he also wrote the song "Welcome to Duloc."[3]
In 2015, Darnell co-founded with Maureen Fan, a former vice president of games at Zynga, a Redwood City, California-based virtual reality studio Baobab Studios to create animated virtual reality short films.[5] Darnell serves as Baobab's chief creative officer, while Fan serves as its CEO. For the studio, Darnell wrote and directed short VR films, Invasion! (2016) and its follow-up Asteroids! (2017), featuring two comedic aliens, Mac and Cheeze.[6][7][8] Plans for a feature-length film based on the characters were announced in 2016 by Baobab and Roth Kirschenbaum Films.[9] Darnell also wrote and directed an animated VR short film, Crow: The Legend, inspired by the Lenape myth. Released in 2018, it features the voices of John Legend, Constance Wu, Oprah Winfrey, Diego Luna and Liza Koshy.[10]