You've riffed that 1959 Coronet Films Christmas Carol Short that starred Basil Rathbone and was introduced/narrated by Fredric March. This is quite interesting, because both March and Rathbone were involved in other versions of A Christmas Carol, the second of which was remade for animation. All three of them have their merits, but have just enough retro-cheesiness to make for good riffs.

In 1954, the anthology program Shower of Stars (sponsored by Chrysler) presented an hour-long musical version of A Christmas Carol starring Fredric March as Scrooge and Basil Rathbone as Marley. Being who they were, the lead actors turned in terrific performances...especially Rathbone as Marley, who conveyed the character's suffering in every word. The script was good, and the music was terrific--being composed by Bernard Herrmann, an accomplished film and classical composer who'd go on to compose for several Hitchcock movies, including Psycho. But being an hour-long version, some things had to be rushed over and condensed. For example, Belle and Ebenezer's breakup (a matter of only a few sentences) happens only seconds after they'd sung a loving duet--with only slight indication that any time has passed. (And for the record, most of the American actors don't even attempt English accents.) Then there's the Christmas Yet To Come sequence. We're all braced for the eerie, robed spectre who will lead Scrooge through the bleak future his present path will lead him to, and what we get is...a myna bird perched on a tree in a graveyard. Said graveyard is the entirety of the Yet to Come sequence. No corpse-robbers cackling over their finds, no debtors relieved that Scrooge is gone and their ruin is staved off, no coming across his own shrouded, neglected dead body, no grieving Cratchit family consoling each other over Tiny Tim's death...Scrooge is the only person we see in this sequence, and it consists of his stumbling around tombstones on a fog-shrouded stage until he finds his own, and then Tiny Tim's, and then awakens in the present. And the whole sequence lasts less than two minutes, and Scrooge doesn't even have any real dialogue during it! So despite its merits, this is somewhat hampered by the limits of its early-television format. (Plus, it was originally broadcast in color, but the only surviving prints are in black-and-white.)

Two years later, Rathbone himself would star as Scrooge in The Stingiest Man In Town, another musical version co-starring Vic Damone as young Ebenezer and the singing group The Four Lads as a sort of Greek chorus. Again, it was broadcast in color but its only surviving print is in black-and-white--a kinescope that was lost for some time. Again, the music's good and the vocal performances are stunning (Belle's played by a trained opera singer), but the limitations of the early television format are apparent.

Then, in 1978, The Stingiest Man In Town was remade by Rankin-Bass--in traditional animation, not stop-motion as so many of their specials were. It was cut down to an hour but nearly all of the songs from the original were preserved. This was around the same time R-B made The Hobbit, and many of the character designs looked like they could have stepped straight out of The Shire. There were quite a few well-known voices--Walter Matthau as Scrooge, Theodore Bikel as Marley, Dennis Day as nephew Fred, and Robert Morse as young Ebenezer. But there was a rather glaring addition. To make it more kid-friendly, and to keep up the tradition of every Rankin-Bass special having some kind of celebrity-voiced narrator, there's a Jiminy Cricket-like insect narrator named B.A.H. Humbug, voiced by Tom Bosley. The result is a strange mixture of Dickensian seriousness, good music and vocal performances, and pseudo-Disney whimsy.

All three of these have just enough cheesiness to give us some hilarious holiday riffs, but are charming enough to be good holiday fare as well.

From Wikipedia:

Supertrain is an American adventure-drama television series that ran on NBC from February 7 to May 5, 1979. Nine episodes were made, including a 2-hour pilot episode.

The series took place on the Supertrain, a nuclear-powered bullet train that was equipped with amenities more appropriate to a cruise ship. It had luxuries such as swimming pools, shopping centers, a gym, library, medical center, and a discotheque.[1] It was so big it had to run on very broad gauge track. Though it had a rated top speed of 250 mph (402.34 km/h), and cruised at 190 mph (305.78 km/h), the train took 36 hours to go from New York City to Los Angeles; this would put the train's average speed at around 80 mph (128.75 km/h), slower than that of Amtrak's Acela Express and well below the speeds of bullet trains in Europe and Asia. (Some episodes state, however, that the train also stops in Chicago, Denver, a fictitious town in Texas and presumably other cities, which would extend the length of the run and thus would require faster speeds.) Much like its contemporary The Love Boat, the plots concerned the passengers' social lives, usually with multiple intertwining storylines. Supertrain was described in a 1979 Variety review, "It's a 'Love Boat' on wheels which has yet to get on track."[2] Most of the cast of a given episode were guest stars. The production was elaborate, with huge sets and a high-tech model train for outside shots.
https://www.youtube.com/watch?v=2Av1P8cFVw8
why Rifftrax should riff on it:
1. a pool on a train!
2. a disco on a train!
3. a nuclear-powered train!
and bonus...
it's 1979! It needs to be riffed!

The time is waaay overdue for a spooky scary funny "Rifftrax Live Halloween Extravaganza." This would be a mixed bag of Halloween themed shorts, cartoons, weird short films, vintage spook show trailers, and maybe some really terrible monster/science fiction trailers, all done in the format of an olden days type 'spook show.' These spook shows used to include the audience as part of the fun. Monsters running down the aisles, cheesy fake ghosts floating over the audience, etc. With time permitting you could even include a short really horrible old creaky horror movie that is down on it's little knees begging for the overdue riffing attention that It truly deserves. Special guest riffers are requested, yes please, as well as other spooky surprises.
Pull out all of the stops on this one boys, and riff the yell out of everyone.

You know you're in trouble when they don't even get the title right. (It's A Christmas Carol, not THE Christmas Carol. ...Actually, according to Dickens it's A Christmas Carol In Prose, Being A Ghost Story Of Christmas, but who calls it that?)

And you're in even MORE trouble when they misspell the main character's NAME in the opening credits. (Who is this "Ebeneezer"?)

This was an early television production--and I mean EARLY, as it wasn't even the fifties yet. It's a half-hour short that was meant for syndication on 22 stations across the country on Christmas Day of 1949. Vincent Price introduces and narrates, and does his usual good job, but if you thought his old horror movies were the cheapest and cheesiest things he'd ever been in, you've got another think coming.

As is common in these early TV productions of A Christmas Carol (see my submission on two made-for-TV musical versions from the fifties), most of the American actors don't even bother with English accents. In fact, Scrooge sounds more like a prospector from the Old West, or like Abe Simpson. (And looks more like Ben Franklin.)

The entire Christmas Past sequence consists of the Ghost (an unremarkable guy swathed in a white sheet) showing Scrooge his boyhood at school--no visit from sister Fan, no visit to Fezziwig's party, and his breakup with his fiancee isn't shown either; the Ghost just mentions to Scrooge how he drove away the woman he loved. That's the entirety of the whole segment. I guess they couldn't afford to pay an actress to play Belle.

The other sections are similarly shortened--Christmas Present is only a visit to the Cratchits, and Christmas Yet to Come (the Ghost here looks like a guy in a cheap homemade Jawa costume) actually allows us THREE scenes--the Cratchits again, a glimpse of Scrooge's former colleagues, and his gravesite.

The acting is about as wooden as a Groot family reunion--the best actor in the whole thing is Vincent Price, and he isn't even technically part of the story! One wonders what a version with him playing Scrooge might have been like. There are other notable things about this cast--for one thing, there's a nine-year-old Jill St. John, under her real name of Jill Oppenheim, as one of the Cratchit daughters. And Scrooge is played by Taylor Holmes, who had some good character roles in high-profile movies like Gentlemen Prefer Blondes, and voiced King Stefan in Disney's Sleeping Beauty--all with far better performances than he turns in here.

This is about the same quality as many of the Christmas shorts you guys have done in the past--and, as such, a perfect candidate. See for yourself here: https://www.youtube.com/watch?v=G531q5KKVVU

This ... this movie. Gene Kelly and Olivia Newton John somehow maintain their dignity during this glorious dumpster fire. The plotline is roughly "What if we signed ELO and shoveled a ton of money into a movie that was put in front of the cameras with no script? Let's have four or five different styles of dancers that have no idea what the others are doing, and film them all together with no thought to blocking. And tie it all together with a ham-faced cipher that we're going to make the romantic lead!"

See the film that asks the question, "Can we make Roller Disco cool?" (And that answers it with a resounding "No, we can't. Nobody can. We honestly don't know what got into us)

Greetings! I have been a fan of yours since MST3K was on SciFi. Last time I made a suggestion it was for Miami Connection. Imagine my delight when you riffed it later that year!😁

Anyway, I think 13 Ghosts would be perfect for riffing. Of course I don't mean the remake with Tony Shaloub--which I didn't even realize WAS a remake! I caught it on Turner Classic Movies once during Halloween. It is just cheesy enough to be riffable, but not so awful that you can't bear to watch it. I loved it, and was actually interested in how it was going to end. The only thing it has in common with the remake is that there are 13 ghosts and the cast has to wear special glasses to see the aforementioned specters. I have found a trailer that I hope will show just how awesome it would be. Enjoy!

https://youtu.be/Ocdb4qI2PqE