Fun thread. Like many here, I was about 7 or 8. Combination of the handwriting thing (my mom's is very distinctive - though she always made sure that the wrapping paper on gifts from Santa
never also appeared on gifts from any one else) and scuttlebutt on the playground at school I suppose.
Here's a related question, though, for those of you who figured it out yourselves: how long before you let your
parents know you "knew the truth"? I waited 3 or 4 years, because
I didn't want to ruin
their fun.
Plus, I had a younger brother, and didn't want to spoil it for him - not that there weren't times when I was sorely tempted; the little brat.
Dad took the news stoically, but I swear I thought my mom was going to burst into tears.
I will say my parents were slick enough to never get caught. One time, they even assembled a rather complicated race track that took up half the living room.

I can appreciate the effort that went into that, knowing it wasn't "magic."
Yeah, that amazes me to this day. Even though I knew, and even when I tried my darndest to stay awake just to catch them at it, somehow I always conked out and never heard them sneaking around. I remember so many times trying to keep my eyes open and then waking up at like 3:00 in the morning and running to the livingroom, only to see all the presents already under the tree. Talk about a "D'OH!" moment.
I have long suspected that they were putting some kind of little kiddie tranquilizers in our cookies and milk on Christmas Eve.
At one family gathering after my brother and I were all grown up, my parents confessed that one Christmas Eve they'd had a little too much Christmas cheer and knocked over the tree while trying to put all the packages underneath. They were sure they were busted, but we never heard a thing.
Again, I think the tranq's are the only answer.
