My oldest niece is at the stage where she can sing "Rudolph, Rudolph, shiny nose" repeatedly. With prompting she'll get a few more words, and she loved my "Like a lightbulb" addition, which she later garbled into "Rudolph had shiny nose.. LIGHTBULB!"

She was most distressed when she realized that I only knew the first verse of Frosty the Snowman. I'll have to do better for next year.