The Worst Christmas Song I can Imagine:

"Don't You Love The Christmas Spirit You Get When You Come Home For the Holidays and Unwrap the Gifts with Grandma and the Reindeer To Remember The True Meaning of Christmas?"

A composite, as you can notice, of many different songs.

(P.S. If you read this, Grandmas D. and P., just I have nothing against you. I have something against generic grandmas scattered about the place.)