Song Trivia:
Often credited to Brenda Lee, I Saw Mommy Kissing Santa Claus was recorded and released by Jimmy Boyd in 1952. Boyd was only 13 years old when he recorded this song. The original recording by Jimmy Boyd reached #1 on the Billboard charts in 1952

When released, some people thought it was a little too risqu , the thought of a married woman, possibly having an affair. A closer listen implies that Santa Claus is actually the child's father, but this didn't stop radio stations in some cities, including Boston, from banning it when it came out. Columbia Records appealed to the Council of Churches to clear the song where it was banned. The tactic worked, and it became a Christmas favorite.
~Source: songfacts.com