How about "Baby, it's cold outside ... cuddle up with a quilt"? I like the idea of having "cuddle" in there, but for me the second one conjures up a picture of me watching the parade and someone I don't know coming up to me trying to cuddle. Probably not what most people are getting out of it, but it was what came to my mind when I read it.
For the visual, I think it'd be cute to have dogs and cats sleeping on top of quilts. Or maybe reindeer since it's for Christmas.