Illusian

Illusian (イリュジャン) is a green robot enemy in Mega Man 9, that appears in Wily Stage 2. It flies from one side of the screen to another, periodically stopping to create fake blocks. Fake blocks look solid, but are actually nonexistent.

Trivia
Its name is derived from the word "illusion" (イリュージョン iryūjon).