So Saturday I ran this game, you know, and tied a module in for the adventure. A module that was very fond of monster manual 2.
It had the teratomorph, which some complete...ly different thinking person reckoned to be CR16.
Anyways, I will say what I liked about the teratomorph encounter..
Transformation: Target is changed as though targeted by Polymorph Any Object, changed to an object of DM's choice.
The DM chose to ask his five-year-old son to name something, which ended up being a "spray bottle". To keep it in appropriate tech level this became one of those things with a bulb that is squeezed to spray perfume (someday I will research before I start typing my blog)
fortunately the change was temporary, per the spell descriptor.
You see, every time the teratomorph hits with it's nearly unavoidable melee slam, the DM rolls on what I call the "random cornhole table", with such lovely things as 2d4 constitution drain, d6 strength or dex drain, change into a cosmetic appliance, or DEATH. Not just quick-trip-to-the-druid's-office death, this is 18th-level-cleric-and-25000-gp-worth-of-diamond DEATH. I rolled high on th table and this happened to Epik in the first round. I decided that this was a bit extreme(as is everything about the teratomorph), so he came back the next time I rolled on that table, with his skin turned a randomly chosen blue.
I am not even mentioning half of the insanity of the teratomorph.
But as I said, I will focus on the positive. Changing a player character into a spray bottle was hilarious. Asking a small child to choose the punishment of a character is like asking Ray Zelinski to choose the form of Gozer the Destroyer - pure fun and deliciously ironic to have a half-orc suddenly be a cause of good smells.