I figured it out when I noticed, at the age of 7 or 8, that "Santa" uses the same wrapping paper as my mom. When I asked my mom about it, she tried to deflect the question, which in retrospect I find funny and adorable.

I actually have video of this, as my father had just bought a video camera (the old fashioned kind that plugged into a portable VCR on the floor) and filmed the whole thing on VHS.