This animated movie is lesser known here in the U.S., but I know it’s quite popular in the U.K. and Finland: The Snowman, from 1982.
I heard about it recently because I heard the beautiful song Walking in the Air on the radio, and the announcer described the movie. I went and looked on youtube, found it and watched it a few days ago. It’s a lovely children’s movie and that song is a winner.
A bit of a stretch: Mars Attacks! (The reason all of the victims’ skeletons are red or green is because the movie was scheduled for a Christmas release)
I watched this based on the recommendations here and really enjoyed it! It was well done and could’ve been a theatrical release. Thanks!
I have neither seen nor heard of this movie before this thread. But after reading your post, I thought to myself: That sounds like a movie MST3K would do.
So I googled it, and sure enough, they did it. 
I’ll be watching this tonight.
Thanks for sharing.
One unconventional Christmas movie that I like is Tokyo Godfathers. The three central characters are homeless people in Tokyo, and the movie is about the miracles that happen to them at Christmas time, including reconnecting with each of their families.
This may not qualify as “lesser known,” but it’s one of my favorites. The Bishop’s Wife(1947) with David Niven as an uptight Bishop concerned with fundraising and administrative matters, Loretta Young as his slightly neglected wife, and Cary Grant as the angel who is sent to help them out and who has to be reminded (a) that it’s a temporary assignment and (b) that technically he isn’t corporeal. Utterly charming, especially when Cary and Loretta ice skate and he persuades her to buy a new hat.
I know there was a remake with Denzel Washington called The Preacher’s Wife. I never wanted to see it (although I love Denzel), mostly because remakes usually don’t work out. If someone tells me it was good, I’ll give it a look.
Conquest of Space
I agree, it’s a fun movie. The highlight is Kurt as Santa doing a jailhouse Elvis impression singing It’s Christmas Time Pretty Baby.
Watched it this evening. Very clever. Three thumbs up. 
I agree, that is a highlight. But my favorite moment is when a disbelieving cop hears jingling bells in the distance and asks, “What’s that sound?”
Santa (Kurt) tells him, “Sleigh bells. Are ya listenin’?”
I know it’s a bit late, but I wanted to add another +1 for Netflix’s The Christmas Chronicles. Good stuff, with a wide audience appeal.
I resisted watching for many years as the title was too religious for me I thought. I have no problem watching other comedies with God in them, it might not have registered as a comedy with me. Since seeing it for the first time maybe five or ten years ago, it’s definitely in my top five Christmas movies. Being a big Cary Grant fan is likely why, though the rest of the cast is great too.
A true “lesser known” is Rod Serling’s made for TV version of A Christmas Carol, titled A Carol For Another Christmas…
Contemporary to 1964, and nightmarish a la Rod Serling.