The ipod in Sloan's car has been set to Christmas music, so we always listen to it as we're driving. He sings along. And changes the words. To weird words. Here's a helpful scene to better imagine the weirdness...
In the car, Sloan singing to the tune of White Christmas:
Sloan: I'm dreaming of a white Christmas
Just like the ones I used to know.
Where the treetops glisten, and children listen
for once in their miserable little lives...
Julia: BABY. That's terrible!
Sloan: Laughing uncontrollably
Julia: Switches song To the tune of The Christmas Song (Chestnuts Roasting...): Sloan: They know that Santa's on his way; He's loaded lots of toys and goodies on his sleigh. And every mother's child is on the prowl...
Julia: YOU ARE A FREAK!! pounding on the car window GET ME OUT OF HERE!
Sloan: Laughing. Uncontrollably.