Here's a strange one for you, internet:

One of our cats has some very strange bathroom habits.

He executes #1 like a normal cat, but when it comes to #2, he'll spend
2-3 minutes digging in the litter box and scooting litter around with
his paws and also WITH HIS FACE.  He's done this since we got him as a
9-week old kitten. He'll then take care of his business and make a
show out of burying his poop, spending another minute or two "cleaning
up," which usually amounts to shuffling more litter around and
scraping the sides of the litter box till the liner is in tatters.
He's emerges from the litter box with his cute black face covered in
white dust. Aggh!

I've looked this up to no avail, not a mention anywhere.

Here are the facts--maybe someone out there has had this problem
before or can help us solve this mystery?
================================

He's just about 6 months old, getting fixed next week.

He shares our house with a female kitten about this age.  They get
along very well, neither of them is a bully, and though they play a
lot, they've never been in a fight.

We are absolutely religious about cleaning the litter box. We do it
every morning and every night, so it's not an issue of litter box
neglect.

When we realized he had some litter box issues, we changed our litter
from a wheatgrass-based litter to World's Best Cat Litter. This had no
effect on his behavior.

We're using the biggest littler box we could find. Not hooded, not
automatic, just a plain old litter box.  We tried two other types of
boxes as well, no effect on his behavior.

We would never scold him for this behavior, the last thing we want to
do is have him develop a negative association with his litter box.

We got them both from a rescue group.

It doesn't seem as though he's playing in the litter box.  He's
absolutely serious as he goes at the task of out burrowing into the
litter with his whole face until he finds just the right spot.

He displays some other odd behaviors:  He scrapes at his food bowl and
place mat incessantly, more "cleaning up" behavior.  He also made
constant attempts to nurse off our female kitten, but has recently
outgrown that behavior.  Poor guy must have had a rough start.

Our other kitten is just fine.

Please--if you've got any ideas for us, it would be much appreciated!
We love him to death but are tired of wiping him up after every trip
to the bathroom!

THANKS.