An anonymous reader quotes Engadget: Dive into the Easter egg section on your EV and you'll discover a reindeer button that invokes a Santa Mode. To say it brings a Christmas vibe to your car would be an understatement. It turns your car into Santa's sleigh on the dash display (and other cars into reindeer), but that's really just the start of the flourishes. The new mode plays the late, great Chuck Berry's version of "Run Rudolph Run" when it first kicks in, for one thing. You'll also hear sleigh bells when you invoke a turn signal. And if you're fortunate enough to have a car with Autopilot, the road ahead will suddenly turn icy.
The article includes a video showing that the voice command to enable Santa mode is -- of course -- "Ho ho ho."

Engadget calls it "one of the perks of owning a Tesla in the first place. The combination of all-digital displays and frequent software updates lets Tesla add little delights that you couldn't get if you had to stare at an old-school instrument cluster."