In the THQ game, Scooby-Doo Night of 100 Frights, there seems to be an easter egg that I hadn't encountered before... because there's basically a 1 in 365 chance of seeing it.
On November 5th, Guy Fawkes Day, fireworks can be seen and heard in the night sky as Scooby-Doo searches for Scooby Snacks and tries to solve mysteries. It's constant, so it's minorly distracting... it triples the normal amount of noise put out by the game while my kids are playing it.
Still, it's nice to find something new about the game... there isn't a lot of documentation online for kids' games.