At birth, since I don't remember ever believing in Santa.How old were you and how did you find out Santa isn't real?
Don't believe everything you see on the internet.just today... sniffle sniffle
I did the same thing when my daughter was about 1-2, only it was a Donald Duck mask. I thought she'd think it was funny, but she thought it was real and started screaming. And this was a kid who never screamed. I was horrified, ripped off the mask, kept saying, "It's me, Mommy," until she calmed down, and then I said "Bad mask" and started hitting it, overcome with guilt by that time, and she repeated, "Bad mask" and started hitting it also. Amazingly, she grew up to be a perfectly normal person anyway, and is now an adoring, sensitive grandmother of two wonderful kids. So they do survive at least some of the dumb things we do.When I was 2 -3 my grandad dressed up as Santa and it had this horrid looking plastic mask.
I screamed my head off and literally began climbing over Mom's head to get away from him
Grandpa took off the mask and crooned my name and kept saying "It's me, Grandpa"
Once I reached for him I said "My Santa Grandpa" so by accident I learned early.
I had my very own Santa for all his years.

you know , my daughter felt the same as you when i told her ...I'm not sure how old I was, but it was traumatic. I felt betrayed by my parents, and I cried.