Bump because I know popple's here and has the game.

Here's a list of the enemies you should've gotten blitties from in Peach's Castle (don't know all their names, but whatever)
-Fawfulbot
-Sleepy Pig Golem
-Dark Fawfulbot
-Dark Treasure Box(?)
Tell me if you've encountered these enemies and claimed their blitties. Also, i'm not sure if the Darl Treasure Box has a Blitty; don't recall ever getting one out of it.

Dark*

Gahh, I keep battling those enemies, but nothing. I've searched *crag*ing everywhere. I tried battling everything I see.
But nothing.

Alright, I think you're missing Dark Mechafawful 1.5. To encounter it, you must fight a Dark Mechafawful that's not alone, destroy it's body, and let it regenerate. It will then become a new enemy. After that, see if it has a Blitty for you.

Um, how many turns do I have to wait to regenerate. It's taking a long time.

I have no idea. All I know is it said he'll regenerate and become a new enemy.

the vacuum button actually doesn't blink when a blitty is around, and yes, the treasure box gives a blitty...
i don't remember having to fight a dark mechawful 1.5 to get a blitty

He already got it, don't worry.