I had an idea on how the Muppet Monsters could have been in this too( It would also have been a good way to bring back old characters
):
It's like this... After Fozzie comes into the house from being with the snowman, he closes the door only to hear the doorbell ring once more. He opens the door and it's a delivery man (either Jerry Nelson or a whatnot Muppet) and He says "Fozzie Bear? I have a delivery for you. Please sign here.". Fozzie looks out onto the lawn and he sees a huge cage filled with Muppet Monsters. Boppity, Sweetums, Gloat, you name it (Only from TMS). And it also turns out, they're all wearing Santa hats and singing Christmas carols. By the time they're done Sweetums and thog manage to break a hole in the back of the cage and Fozzie tries to run away but ends up getting trampled by the mob of monsters making their way into the house.
TA-DAAAA! So whad'cha think. Awesome, is it not?