For those of you asking, "What's an Easter Egg?" - an Easter Egg is the name given to little surprises hidden in software. It used to be that low-level programmers would hide their names in software so that when someone hit the right combination of keys (or something similar) their names would appear. Or, when a certain date was reached, something would happen (like a Christmas tree appearing on Christmas).
Nowadays, you can find these things in DVDs as well as software, although the studios put them intentionally into the DVDs.