Boo! (1980 variety special)
This hour-long Canadian variety show is very nearly the Halloween equivalent of The Star Wars Holiday Special. At least it has its share of cheesy, dated charm, and unlike the SWHS, it doesn't pretend to be anything more than a variety show (no flimsy plot to link the songs and sketches together). It was filmed for Canadian TV in 1980 (when some remnants of the 1970s were still hanging on--hence, the disco-ish theme song and overall 70s-ness of it all). But it was shown on American TV a few times in the early 80s--the link I've provided was from a 1982 Chicago airing, and I'm pretty sure I saw it on Philadelphia-area TV, one Saturday or Sunday afternoon, in 1983.
The premise: the classic Universal monsters, along with a slew of assorted aliens and BEMs, do a variety show full of comedy sketches and a song or two. (Dracula makes a wisecrack early on about variety being "dead", which made it the perfect vehicle for an undead host.) Most of the jokes are sub-dad jokes or so dated they barely make sense now, and there's even a somewhat homophobic joke--you know, for kids!--with two robots who didn't know the other one was male.
Of course, you can't have a variety show without guest stars, and this one delivers--Dionne Warwick performs her then-recent hit "Deja Vu" (and pretty well, too) and Rip Taylor shows up for his usual brand of "comedy"--confetti and all.
There's also one other semi-familiar face (or, at least, voice)...the Wolf Man is played by Peter Cullen, best known as a voice actor and the voice of Optimus Prime. (He is, after all, Canadian.)
This show's overall cheesiness and datedness should provide LOADS of riffing fodder--certainly, the riffs would be funnier than most of the jokes! After all, you've shown you're good at lampooning 1970s Halloween specials with The Night Dracula Saved The World...
Here's a link to check out (complete with 1980s commercials...)