The non-fluffy animals in life

Right now I'm taking Organismal Biology and we have come across several really cool animals throughout the course.  One is a parasite, Cymothoa exigua, that eats the tongue of its fish host and then plays the role of the fish's tongue until it decides to leave, causing the fish's death.  I'm really unsure of the mechanism of the parasite acting as the tongue but once the parasite decides to live there, the fish has zero chance without it sticking around.  This other one I came across while doing research for one of my papers.  Elysia chlorotica is a sea slug that feeds on algae until it stores enough chloroplasts that it no longer needs to eat.  Because of the abundance of chloroplasts, the slug obtains energy from sunlight just like plants do.  So it's part animal/part plant/part really f-ing cool.