Batman Gotham Knights

Barbara: (answering Bruce Wayne's question "What are you doing tonight?") The same thing we do every night, Pinky.
This exchange is a variation of the lines that begin and end every episode of Pinky and the Brain, an animated series about two lab mice who spend each night trying to take over the world. At the time this episode first aired, both of these series aired on the WB, so this was probably an in-joke. Naturally, Bruce had absolutely no idea what Barbara was talking about.