This is too much fun to pass up.
I have two favorite characters that I would like to use for this, and they are Hercule Poirot and Miss Marple.
Since this is my script, they'll both know each other.
Christmas music would be playing, the house would smell like freshly baked gingerbread (now I really want a cookie), as the two of them decorated the tree with tinsel and light, they compared the different cases they had come up against, along with their triumphs and defeats. Then just before they could try to call the other ones bluff, the doorbell would ring ushering in some unfortunate in need of their help, and thus would be the beginning of the great Christmas team up.