Lou is one of Harley Quinn's pet hyenas in the Batman animated series. Along with his companion Bud, Lou provides comic relief and assists Harley in her various criminal escapades. The character is notable for his loyalty and mischievous behavior, often causing chaos for Batman and Gotham’s citizens. Lou does not have a traditional human role but is an important part of Harley Quinn’s story, highlighting her eccentric personality and the unpredictability she brings to the series.