Has anyone ever done black pastel x lesser?
Yes it has been done.

Or black pastel x clown?
The Cinny Clown as been done ( http://www.grazianireptiles.com/gall...1242235929.jpg) so I would not be surprised if we soon see a Black Pastel Clown

What does a pastel x black pastel look like?
It's Black Pewter

And black pastel x black pastel can produce a super black, right?
Yes