Leucochloridium paradoxum - Parasitic worm that infects snails, manipulating their eye stalks to resemble caterpillars which attracts birds to eat them
I think you're just focusing on the pooping cycle. The part where the parasite possesses the snail and creates this elaborate display with the eyes to draw its real intended host/target is what's fascinating.
i don't think so (:
toxoplasma IIRC alters a host's behavior in favor of cats, so that it can infect those - since cats are the only ones it can reproduce in. not as colorful and funky as the exapmle here, but similarly clever/complex