Mariah Carey Wears ‘Alvin & The Chipmunks’ Costume at Horror Nights

Mariah Carey must’ve watched “The Nightmare Before Christmas” recently … ’cause she’s blending Christmas and Halloween perfectly at Universal’s Halloween Horror Nights!

The singer-songwriter hit the annual Halloween bash earlier this week, outfitted in an “Alvin & The Chipmunks” costume … pretty hilarious considering the little rodents have almost as much Christmas clout as MC.

In the vid, Mariah’s milling around The Wizarding World of Harry Potter … with enough security to protect from any vampires or werewolves who might want to take down the Queen of Christmas.

BTW … we’re told her kids were with her at the event — but, they don’t appear to be in the vid. Unclear if they were grabbing a Butterbeer, but sounds like the whole crew enjoyed an evening together.

As we’ve told you … Mariah’s already changed the calendar on IG — going from Morticia Adams tangoing with Gomez to her normal Mariah Claus ensemble for the Christmas season in a clip she posted minutes after November 1 hit.

Mariah’s got an even more chaotic Christmas season than usual BTW. Next week, she begins a string of 21 shows that will end just before Christmas — with appearances in Hollywood, Dallas, Atlanta, Boston, Baltimore, Philadelphia, Brooklyn and more scheduled.