'He see's you when you're sleeping... He knows when you're awake...'
It certainly can be interpreted as something VERY disturbing doesn't it?
Well, Rudolph the Red-Nosed Reindeer is about physical defect, bullying, social outcasts, how everyone seeks favor from those with something to offer(like money, power, influence, or in this case rise is social status)and etc.
"I Saw Mommy Kissing Santa Claus" is obviously about a kid finding his dad in a Santa outfit kissing his mom but is very easy to imagine... other things and interpretations.
