Last week Zach came home singing Happy Birthday. I don't really think it was Katia's birthday, but he is certain it was. When he sings it to Trinity he now says "Happy Birthday, Trick-or-Treat". He will also just wish you a Happy Birthday at random times too. Since I LOVE to celebrate my birthday anyway this is working out very well for me when he turns to me and says "Happy Birthday Mommy!". I just melt.