The first half of the opening and closing song is an electric guitar rendition of "Oh What a Merry Christmas Day" from Mickey's Christmas Carol (1983).
There is technically a 3rd part to this Christmas Special, which actually makes this episode Part 2 and the next one Part 3. The lead-in to this where the Nerd discovers the Christmas present that turns out to be Home Alone 2 for NES is actually the finale of A Very Nerdy Non-Canonical Captain S Christmas, which was a crossover between the AVGN and Captain S, who were both big internet stars at the time, with content revolving around video games. All 3 parts can still be viewed on Youtube as of November 2022.