In 1941, Maltese was hired by Leon Schlesinger Productions, which three years later became Warner Bros. Cartoons, Inc. (Maltese had actually appeared on camera in the 1940 Porky Pig cartoon You Ought to Be in Pictures as a live-action guard at the Warner Bros. entrance gate, who winds up chasing the animated Porky around the Warners lot). The first cartoon he wrote for Warners was The Haunted Mouse (1941) by Tex Avery. He first worked for Freleng until 1948, but after that he worked mostly for Chuck Jones, contributing stories to other directors at times, including Robert McKimson. He and Jones collaborated on classic cartoons like the Academy Award-winning For Scent-imental Reasons and the animated public health documentary, So Much for So Little which won that same year for "Best Documentary Short Subject." Maltese was also the voice of the Lou Costello-esque character in Wackiki Wabbit. Some of his earlier works include The Wabbit Who Came to Supper and Fresh Hare, Hare Trigger (which introduced Yosemite Sam), Baseball Bugs for Freleng; Bear Feat, Rabbit of Seville, and Rabbit Fire for Jones. Some of his best-known cartoons are Feed the Kitty, Beep, Beep, Rabbit Seasoning, Don't Give Up the Sheep, Duck Amuck, Bully for Bugs, Bewitched Bunny, From A to Z-Z-Z-Z, and Beanstalk Bunny. These were all directed by Jones. He also worked on One Froggy Evening, the first appearance of future Warner Brothers mascot Michigan J. Frog. Some of his later cartoons included Ali Baba Bunny, Robin Hood Daffy, the seminal What's Opera, Doc? and Duck Dodgers in the 24th Century for Jones and Person to Bunny (the final time Arthur Q. Bryan voiced Elmer Fudd) and Here Today, Gone Tamale (the only Speedy Gonzales cartoon he ever wrote) for Freleng. Maltese also collaborated with Jones on the 1960s Tom and Jerry theatrical shorts for MGM. From 1958 until 1970, he worked at Hanna-Barbera Productions on television cartoons such as The Quick Draw McGraw Show, The Flintstones, The Jetsons, and Wacky Races. Maltese also did scripts for comic books published by Western Publishing, including for many of the same Warner Brothers and Hanna-Barbera characters whose animated exploits he scripted.