Batman: The Animated Series was a game-changer for cartoons in the 1990s. Up until its premiere on Sept. 5, 1992, animated superhero shows were whimsical children's entertainment. Heroes and villains were often two-dimensional as the cels they were drawn on. Batman: The Animated Series took a considerably different approach.
Source:https://www.cbr.com/batman-the-animated-series-heartbreaking-episodes/