Ran this the Wednesday before Xmas instead of my usual D&D. Had 9 PCs. Everyone LOVED it! Took the original Dead Letter scenario, added in secret TINSC (There is no Santa Clause - "tin-sink") Part to the Anti-Christmas villian set, with "Postal Inspectors" equiped with 'The World As It Really Is' ("TWAIRI") ray guns that give -1 to Xmas Spirit score. A zero and an elf simply becomes a cynical short person. Also equipped the Inspectors with "Postal Regulation" book grenades - they explode (10ft radius) papering the targets with postal reg pages that stick to them, immobalizing and blinding the target for 1D6 turns.
Will see if I can work up a Valentine or Easter adventure next!