A Christmas episode of the Twilight Zone?  Yes, such a thing does exist.  In Night of the Meek, an unemployed man (Art Carney) is given a chance to be Santa Claus.  This is a wonderful episode that truly captures the spirit of the season.

Night of the Meek was written by Rod Serling and directed by Jack Smight.  It was originally broadcast on December 23rd, 1960.