No, not recently. I can make some guesses though...
Mindflayers can turn almost anything they think might be useful, a Mindwitness has shown up in the comic, and I'm sure there'll be a Brainstealer Dragon at some point - because it's Larian, and it'll be fun!
I'd like to meet an Urophion too, one we can feed an enemy to and then chat with.
Sometimes Mindflayers have resdiual memories of their victims, so a MF that has a dim recollection of "wanting a pony" might act out on that impulse. And 'flayers riding brain-eating tentacle-headed horses is cool anyway.