Back when they were just starting out, Tellme Networks, Inc, the company responsible for a large portion of the speech recognition-enabled phone systems in use today, started a service where you could call 1-800-555-TELL and get news, weather, stock quotes, and other stuff by just speaking.
One night, I was calling 800-555-TELL to try out my new VoIP connection from Vitelity.net, and it made a significant recognition mistake.
I had spoken "blackjack", hoping to play their voice-enabled blackjack game. Instead, the system thought I said "Festivus", and sent me to a category that none of the menus listed, and that I never knew existed. It played the following quote from Seinfeld:
Frank: ...I haven't celebrated Festivus in years! What is your interest?
Kramer: Well, just tell me everything, huh?
Frank: Many Christmases ago, I went to buy a doll for my son. I reach for the last one they had--but so did another man. As I rained blows opon him, I realized there had to be another way!
Kramer: What happened to the doll?
Frank: It was destroyed. But out of that, a new holiday was born. "A Festivus for the rest of us!"
I was delighted to find this easter egg, and ecstatic when Google told me I was probably the first one to discover it. You can try it yourself: just call 1-800-555-8355, wait for the "Main Menu" prompt (you can interrupt the listing of categories) and say "Festivus".