A Boy and His Sister: A Dexter's Laboratory Movie

A Boy and His Sister: A Dexter's Laboratory Movie is a 2026 American computer-animated adventure comedy film directed by Genndy Tartakovsky (creator of the original series) and written by series writers Paul Rudish, Amy Keating Rogers, Michael Ryan, and Walt Dohrn. Candi Milo, Kat Cressida, Eddie Deezen, Jeff Bennett and Kath Soucie reprise their roles from the series; accompanied by Mckenna Grace, Martin Short, Charlize Theron, Jim Parsons, and Dan Aykroyd. This is the first computer-animated feature film from Cartoon Network Studios, with co-production by Warner Animation Group.

A Boy and His Sister had its premiere in Hollywood on March 25, 2026, and was released theatrically in the United States for the series' 30th anniversary on April 10, by Warner Bros. Pictures. It grossed $150.2 million on a $90 million budget. The film was met with positive reviews, with critics praising the voice cast, humor, and heart, while the choice of computer-animation was mixed.

Plot
Dexter, having graduated from Huber Elementary and moving to Huber University, receives a Nobel prize for his invention that ends world hunger; an invention he had been working on in secrecy due to his childish older sister, DeeDee, who had ruined several of his inventions from the start. DeeDee, eavesdropping on Dexter's pursuits, was heartbroken but determined to sabotage his dreams. As the night of the ceremony had begun, DeeDee had stopped the machine by spitting a wad a gum she was chewing during Mandark's showcase of his visual Mind-Screen invention. After Dexter's world hunger machine had made a good first impression, the machine spits out various amounts of food at the audience. Dexter fortunately stops the machine in time, but discovers the wad of gum in the gears which costs him the Nobel prize. In retaliation and realization that DeeDee was responsible, Dexter blames her and starts a food fights with her.

After the ceremony, Dexter was disappointed and upset about his dream being crushed until he gets a call from the committee that one of their security cameras caught footage of DeeDee spitting her gum into the gears as everyone was oblivious; exposing DeeDee for sabotaging his machine and reinstating the Nobel prize to him. As DeeDee was exposed, she ends up grounded for it. Dexter later enters her bedroom to take pity on her, whereas DeeDee angrily explains that she hates the idea of him going to college and never got the childhood with him; Dexter apologizes for it, but he cannot pass up his opportunity. The next day, the family visits Huber University, and Dexter is amazed by its facilities and classes to his