You might be surprised to learn more St. Nick isn't the only one who made good use of chimneys.  In European recordings it is said witches made use of human fat for magickal means that allowed them to travel through chimneys.

In variations of the tales the devil was the one who collected the fat for his own purposes, then gifted the fat to the witches.

In any case a witch might come down your chimney; likely without a bag of presents.