Walker worked with Danny Elfman on many DC Comics works. She served as conductor for the film "Batman", wrote most of the scores for "Batman: The Animated Series" using a theme inspired by Elfman's, scored the pilot and all the episodes of "The Flash" (the main theme was written by Elfman) and scored episodes of "Batman Beyond" with Michael McCuistion, Lolita Ritmanis and Kristopher Carter. Though her involvement in the DC Animated Universe ended after "Beyond", several of her themes would be used in "Justice League" and "Justice League Unlimited".