Whatever may be the case with the spirits, the initiates who sing "Happy Trails" to them certainly have a sense of humor.
Christmas was set on "VIII Cal. Ian." (i.e. December 25th) long before Pope Gregory's English mission. The letter of Gregory to Augustine is famous and widely quoted. As I recall it advises A. not to supress his converts' urge to make merry, but to direct it into Christian channels. He specifically advises having them build lean-tos out of branches during their celebrations if they are accustomed to outdoor merrymaking.