It's a minor thing, but when I used to read it back in my youth, I know they spoofed I through VIII, but to my knowledge, they've never spoofed Nemesis. Did they have some sort of Super Special that rectified this? It's just one of those things.
Not to my knowledge. Mad magazine tends to spoof the major, well known movies of the moment, Nemesis was a low box office, semi-obscure movie. Even through Star Trek itself was well known, there were bigger movies that year to spoof.
I remember MAD's STV spoof was a one-page thing, with "God" turning out to be MAD Editor-In-Chief William Gaines. Considering how the summer of '89 was in terms of blockbuster movies, you can't blame them for giving TFF short shrift.
I remembered when they had a 1991 Super Special that featured a Star Trek VI spoof. They had a one page Star Trek V spoof preceding it. It wasn't done by artist Mort Drucker unfortunately. Maybe, they'll have a Star Trek-themed Super Special around Star Trek Into Darkness is released in theaters. (BTW, did they do a spoof of JJ Abrams 2009 Trek?) Anyway, I think the spoof-title of Nemesis should have been: Star Blecch: Numbs Us