A Christmas riddle is:

Q: What do reindeer hang on their Christmas trees?
A: Horn-aments.

The “ornaments"/"hornaments" pun has been cited in print since at least 2006.


Boards.ie (Ireland)
19 December 2006, Atlanta (GA) Journal-Constitution, “News for Kids: Santa’s reindeer not the only ones” by Cathy Hulbert, pg. E10:
CAPTION: Reindeer joke: Q: What do reindeer hang on their Christmas trees? A: Horn-aments!

Super Mega Happy Christmas Joke Thread
Hagar
01-Dec-2007 08:27
What do reindeer hang on their Christmas trees?
”Horn”-aments!

Twitter
Q101 FM - Merritt‏
@Q101Merritt
Brian’s Joke of the Day: What do reindeer hang on their Christmas trees? Horn-aments! http://bit.ly/8L8Yt2
11:12 AM - 1 Dec 2009

Twitter
Amanda‏
@hyppychick
What do reindeer hang on their Christmas trees? Horn-aments! #fb
12:01 PM - 4 Dec 2009

The Telegraph (London, UK)
Favourite cracker jokes
A ‘Doctor Doctor’ joke has been voted the nation’s favourite Christmas cracker gag.
1:37PM GMT 15 Dec 2009
(...)
8. What do reindeer hang on their Christmas trees?
Horn-aments!

Google Books
Christmas Crackers
By Matt Wilce
Lulu Press (Lulu.com)
2012
Pg. ?:
What do reindeer hang on their Christmas trees?
Horn-aments!

Google Books
Reindeer Jokes For Kids
By Peter Crumpton
PeteyRF Creative
2015
Pg. ?:
What do reindeer hang on their Christmas trees?
“Horn"-arnents!

Google Books
Gigglers: Christmas Jokes
By Toby Reynolds
London, UK: Scholastic Fiction
2015
Pg. 76:
Q. What do reindeer hang on their Christmas trees?
A. Hornaments.

Reddit—Clean Jokes
What do reindeer hang on their Christmas trees? (self.cleanjokes)
submitted December 18, 2017 by madazzahatterQuality “Ugh” Contributor
Horn-aments.