_{This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2023. The accepted answer to this question will be awarded a bounty worth 50 reputation.}

< Previous Door Next Door >

It was Christmas at Captain Pun‘s house, and he had invited his good friend Captain Clumsy round for lunch. Over the turkey, the stuffing, and all the trimmings, Captain Pun regaled his friend with a series of Christmas-related puns (some better than others):

Who is a caroller’s favourite Disney princess?
Which of Santa’s reindeer is a dinosaur’s least favourite?
What’s a snowman’s favourite chocolate bar?
How do sheep say ‘Merry Christmas’ to each other?
What do you get when you cross a snowman with a vampire?
Who infiltrates the bakery at Christmas?
Why is everybody thirsty at the North Pole?
What’s the most popular Christmas carol in the desert?
What did Santa say when Rudolph got sick?
Who delivers presents to young sharks at Christmas?
What do Santa’s helpers learn in school?
What is the Grinch’s least favourite band?
What do you get if you eat Christmas decorations?

Once Captain Clumsy’s sides had stopped hurting and his tears of mirth had subsided, Captain Pun announced that actually there was one more joke available for his friend to enjoy, hidden somehow in his Christmas tree decorations (“My favourite of all Christmas puns,” he confessed). Captain Clumsy studied the tree and – thanks to his area of expertise – soon had the secret phrase figured out, causing him once more to roll about on the floor, laughing.

Captain Pun frowned. “I haven’t even told you the joke yet!”

TASK: Tell us Captain Pun’s favourite Christmas joke! (And explain how you know this to be the case…)