So many regular series, since the dawn of time, have had Christmas episodes, which I don't consider "specials." Still, I suppose I might as well at least list some of them, in passing. At least the ones I personally remember (even vaguely) seeing; surely there have been many I've seen that I've forgotten, and many more that I've never seen at all. Also note that some shows, particularly animated ones, have episodes broken into separate shorts, not all of which will necessarily be related to the holiday. (This section is for not only Christmas, but potentially Hanukkah or any other wintery/December holidays, including fake ones.) Oh, and while the holiday may play a particularly prominent role in many of the episodes listed here, sometimes it's only a very minor aspect of the episode's plot.

= My favorite Christmas episodes. (Some eps that I don't remember well might become favorites if I ever see them again.)

Everybody Loves Raymond
This had a bunch of Christmas episodes, and I'd probably remember all of them, but I don't really care enough about them to list them individually.

Evil
Season 1: 7 Swans a Singin' (Amazon; IMDb; Paramount+; Wikia)

Family Guy
Season 3: A Very Special Family Guy Freakin' Christmas (Amazon; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia)
Season 9: Road to the North Pole
Season 11: Jesus, Mary and Joseph! (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia)
Season 12: Christmas Guy (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia) This episode resolves a major plot thread that began two episodes earlier.
Season 13: The 2,000-Year-Old Virgin (Amazon; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia) I didn't really like this episode.
Season 16: Don't Be a Dickens at Christmas (Amazon; Christmas Specials Wiki; IMDb; Wikia)

The Famous Teddy Z
Season 1: Seasons Greetings from Al Floss (IMDb)

The Flash
Season 1: The Man in the Yellow Suit (Amazon; A.V. Club; IMDb; TV Tropes; Wikia)
Season 2: Running to Stand Still (Amazon; A.V. Club; IMDb; TV Tropes; Wikia) This so reminded me of "Christmas with the Joker."

The Flintstones
Season 5: Christmas Flintstone (Amazon; Christmas Specials Wiki; IMDb; Wikipedia) Not to be confused with "A Flintstone Christmas"

Foster's Home for Imaginary Friends
Season 3: A Lost Claus (Christmas Specials Wiki; IMDb; Wikia)

Freakazoid!
Season 1: In Arms Way (Amazon; Christmas Specials Wiki; IMDb; Wikia) (one segment)

Fresh Off the Boat
Season 2: The Real Santa (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; Wikia)
Season 3: Where Are the Giggles? (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 4: Do You Hear What I Hear? (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 5: Cousin Eddie (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 6: Jessica Town (Amazon; Christmas Specials Wiki; IMDb; Wikia)

Friends
Season 7: The One with the Holiday Armadillo (Amazon; Christmas Specials Wiki; IMDb; Wikia) There were a bunch of Christmas (or Hanukkah) eps, but this is the only one I really remember.

Futurama
Season 2: Xmas Story (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; Infosphere; TV Tropes; Wikipedia)
Season 3 (or 4): A Tale of Two Santas (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; Infosphere; TV Tropes; Wikipedia)
Season 6 (or 7): The Futurama Holiday Spectacular (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; Infosphere; TV Tropes; Wikipedia)

Gabby Duran & the Unsittables
Season 1: It's Christmas, Gabby Duran! (Amazon; Disney+; Christmas Specials Wiki; IMDb; Wikia)

G.I. Joe: Renegades
Season 1: Homecoming (Parts 1&2) (Amazon; IMDb)

Gilmore Girls
Season 1: Forgiveness and Stuff (Amazon; A.V. Club; IMDb; Wikia)
Season 7: Santa's Secret Stuff (Amazon; IMDb; Wikia)

Girl Meets World
Season 1: Girl Meets Home for the Holidays (Amazon; Christmas Specials Wiki; Disney+; IMDb; Wikia)

Glee (I may not always remember episode plots, but they always have great music.)
Season 2: A Very Glee Christmas (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia)
Season 3: Extraordinary Merry Christmas (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia) I loved Artie's Christmas special-within-the-show.
Season 4: Glee, Actually (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia)
Season 5: Previously Unaired Christmas (Amazon; A.V. Club; IMDb; TV Tropes; Wikia; Wikipedia)

Grimm
Season 3: Twelve Days of Krampus (Amazon; A.V. Club; IMDb; Wikia)
Season 4: The Grimm Who Stole Christmas (Amazon; IMDb; Wikia)

Gunslinger Girl
Season 1: Bambola (IMDb; Wikia)

Home Improvement
Season 1: Yule Better Watch Out (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 2: I'm Scheming of a White Christmas (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 3: 'Twas the Blight Before Christmas (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 4: 'Twas the Night Before Chaos (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 5: 'Twas the Flight Before Christmas (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 7: Bright Christmas (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 8: Home for the Holidays (Amazon; Christmas Specials Wiki; IMDb; Wikia)

How I Met Your Mother
Season 2: How Lily Stole Christmas (Amazon; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia)
Season 7: Symphony of Illumination (Amazon; A.V. Club; Christmas Specials Wiki; IMDb; TV Tropes; Wikia; Wikipedia)

I Love Lucy
Season 6: I Love Lucy Christmas Show (Christmas Specials Wiki; IMDb; Wikia)

iCarly
Season 2: iChristmas (Amazon; Christmas Specials Wiki; IMDb; Wikia)

iZombie
Season 2: Cape Town (Amazon; A.V. Club; IMDb; TV Tropes; Wikia)

Jackie Chan Adventures
Season 3: A Jolly J-Team Xmas (Amazon; Christmas Specials Wiki; IMDb; TV Tropes; Wikia)

Johnny Bravo
Season 1: 'Twas the Night (Amazon; Christmas Specials Wiki; IMDb) (one segment)
Season 3: A Johnny Bravo Christmas (Christmas Specials Wiki; IMDb)

Just Shoot Me!
Season 3: How the Finch Stole Christmas (Amazon; Christmas Specials Wiki; IMDb)

Justice League
Season 2: Comfort and Joy (Amazon; A.V. Club; Christmas Specials Wiki; DCAU Wiki; IMDb; TV Tropes; World's Finest)

Kim Possible
Season 2: A Very Possible Christmas (Christmas Specials Wiki; Disney+; IMDb; TV Tropes; Wikia)

LazyTown
Season 1: LazyTown's Surprise Santa (IMDb; TV Tropes; Wikia)

Lizzie McGuire
Season 2: Xtreme Xmas (Amazon; Christmas Specials Wiki; IMDb; Wikia)

Lois & Clark: The New Adventures of Superman
Season 2: Season's Greedings (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 3: Home Is Where the Hurt Is (Amazon; Christmas Specials Wiki; IMDb; Wikia)
Season 4: Twas the Night Before Myxmas (Amazon; Christmas Specials Wiki; IMDb; Wikia)

Love & War
Season 1: A Christmas Kvell (Amazon; IMDb)

M - R