Once, while running the game I was using mind flayers as the centerpiece villains...but during the session I forgot to bring the stats for mind flayers with me to my friend's house where we were playing. So I flipped through my B/X books to see what I could quickly reskin as a mind flayer-type monster.
I used carrion crawlers for mind flayers.
It makes a certain amount of sense. I mean, look at them, their heads are kinda the same, right?
Their shticks are also pretty similar: they both paralyze you so they can eat you. Worked out just fine.