This just popped in to my head last night - Impossible Creatures.
But unless there has been a change in ownership, I believe the rights belong to Microsoft...

If I do get it right. Am I gonna get it for free? :-)

Assuming you are both correct and first with the answer, yes, that's been how it works so far. :)

Almost needless to say, JMich came up with this same answer 4 days ago... (link)

I WISH it was Impossible Creatures. I have been wanting to try that game for a really long time.

That would be awesome!

Just to be clear, Gray Matter wasn't the game hinted at, correct? (Not sure it has "monsters")

The Enigmatic Hint™ is always for a Thursday release?

There have been cases where the Enigmatic Hint has been for a Tuesday release (like Slave Zero), but I doubt Gray Matter was this week's Enigmatic Hint.

I'm glad the game came but I too am hoping we get a classic this week. Monster Bash would be cool (especially if it means other Apogee classics show up like Wacky Wheels ['less Cascadia has full control], Crystal Caves, Mystic Towers, and Bio Menace as a freebie), but I still hope Titan Quest is it due to the sheer number of votes, or it at least shows up in the near future.

I do have a soft spot for platforming games of the past. New stuff usually doesn't cut it for me (Giana Sisters was a pleasant exception), so more Apogee platformers is always a good thing.

No way on Earth is it this game, but I loved playing it on the C64 - Mail Order Monsters

I'm still hoping I was right, just waiting for Valve Release Time :P
http://store.steampowered.com/app/255070/

edit : ...and it's released on Steam, and not here... yet ;(

Hm, maybe not so much monster mash, and more of an alien mash, but what about <span class="bold">Genewars</span>, the 1996 game by Bullfrog/EA?

Never played it, but it seems to have gameplay features similar to Impossible Creatures where you can make hybrids of alien species (if the game hint is about creating your own 'monsters', Frankenstein-wise). Plus, it's one of the few Bullfrog games not yet on GOG, so it should be possible as far as rights are concerned.