We had no idea! Thanks so much to our pal 'Poncho' for writing in to let us know! He writes:
Dear Joey and Rowdy,
I was watching Rudolph the Red Nosed Reindeer this evening when I saw what looked like a Dachshund leading Yukon Cornelius' dog sled.
After the show, I asked my human to verify the sighting on the Internet and he came up with this screen capture.
That's a doxie up front with a St. Bernard! Ho ho ho!