Christmas movies and specials are a big part of the holiday for me, as I suspect it is for many people. I also have some episodes of my favorite shows that are set around Christmas or New Year that I get out or find streaming every year.
I'm not going to put in where I know the episode can be watched because I know that can change often, and I'm too lazy to come back and catch it up.
Community- Abed's Uncontrollable Christmas, Season 2
I actually like this episode better now than when it first came on. The more I watched the show, the more I liked the character Abed. This entire episode is in stop-motion animation. No one in the group can see the animation that Abed sees, and most of these characters are really not interested in a big, sappy finale, but they realize that it's what Abed needs and they rally around. Abed sings a "sad, quick Christmas song" that, for some reason, gets stuck in my head about once a month, year-round. It's a real earworm.
Community- Comparative Religion, Season 1
Shirley tries to enforce her Christmas values on the group with her Christmas party, and is disappointed when she finds out that Jeff is going to be in a fight. This is the origin of the "Its December 10th!" meme. Also, O Christmas Troy.
Community- Intro to Knots, Season 4
Annie invites the group's history teacher to their Christmas party to try to get a better grade, and Chang ties him up.
Miranda- The Perfect Christmas
Miranda's parents get on her nerves more than usual around Christmas, and when they publicly embarrass her with a song at their Christmas party, she revolts. She goes back to her apartment and invites her friends for a more relaxed Christmas.
The Office (American version)
I'm not going to write a little synopsis for these, because I've watched them so many times that I'll likely start typing a transcript from memory. So I'll just put in some of my favorite bits.
Ranked from my first to least favorite (which is still awesome)
Dwight Christmas, Season 9 (very impish)
Secret Santa, Season 6 (a woman has uslurped my position)
A Benihana Christmas, Season 3 (I miss the days when there was only one party I didn't want to go to.)
Christmas Party, Season 2 (nasty Christmas)
Classy Christmas, Season 8 (epic snowball fight)
Moroccan Christmas, Season 5 (My horn can piece the sky)
Christmas Wishes, Season 7 (my treasures!)
Here's a ranking from Collider, if you want another view, even though mine is better and right.
Doctor Who, in chronological order from the 2005 re-boot
The Christmas Invasion
The Runaway Bride
Voyage of the Damned
The Next Doctor
The End of Time, parts 1 and 2
A Christmas Carol
The Doctor, the Widow, and the Wardrobe
The Snowmen
The Time of the Doctor
Last Christmas
The Husbands of Doctor River Song
The Return of Doctor Mysterio
Twice Upon a Time
The Thirteenth Doctor has New Year episodes instead of Christmas. I have most of the Christmas ones as a playlist in iTunes with all their mini-episodes, so I can watch them in order.
That's all the holiday geeking out that I have time for now, but if there's another TV show with a great Christmas episode, please let me know in the comments.