Ever since I stumbled upon the Undertale fandom, I've been obsessed with the idea of blending AUs with holiday cheer. Hosting an in-game Christmas party in an AU setting? Brilliant! First, pick your AU—'Underfell' for edgy decor, 'Underfresh' for meme-y vibes, or 'Dusttrust' if you want melancholy snowflakes. Modify sprite sheets or use dialogue patches to Christmas-ify characters: Sans in a Santa hat, Papyrus with tinsel-scarf upgrades.
Next, map out party 'locations'—Snowdin’s town square for gift exchanges, Grillby’s with eggnog-themed menus (healing items renamed 'Mistletoe Cider'). Use RPG Maker or UndertaleModTool to add festive battle encounters (imagine fighting 'Krampus Flowey'). Share the mod files with friends or stream the party live, complete with AU lore trivia games. Bonus points for composing a chiptune remix of 'Carol of the Bells' with Temmie vocals.