Batman: The Animated Series Easter Egg - Singing Producers

In the Gotham Knights episode "Holiday Knights," Batman meets Gordon at a diner for coffee. In the corner, next to the door are several carolers, among which are Bruce Timm and Paul Dini, series producer and writer respectively. When the man behind the counter shoos them out, they protest, "But we wanted to sing!" Most people don't recognize the producers when they appear in the episode because not only are they caricatures, but very few people ever actually meet them (Bruce Timm doesn't even go to conventions off the West coast anymore).