>>2
Superflat is supposedly a criticism of the "shallow emptiness of Japanese consumer culture." This would undoubtedly include some anime, but not all.

>>4
I think Henmaru and Tomizawa are considered superflat because of their knack for subverting moe - taking moe artstyles and childish characters and exploring the boundaries of artistic expression with them; pornography in Henmaru's case, realism and perhaps child psychology in Tomizawa's case.

Narutaru might be another anime/manga that accomplishes this, although I don't think it becomes nearly as surreal as Tomizawa's work.