This freakish sea creature might be able to fulfill the hype your pet rock could never live up to.
The video below shows the rock-like Pyura chilensis of Chile and Peru being cut up to reveal its blood-red insides. It’s worth noting, though, that it isn’t actually blood. Its blood is clear and, for unknown reasons, has extremely high concentrations of a rare chemical called vanadium. The red "blood" here is actually the creature's tissue.
A member of the Ascidiacea class, the same as sea squirts, these creatures have a very minimal nervous system, no central brain, are unable to move, and filter feed by sucking microorganisms out of seawater. We'd advise against cutting up such sea creatures (or any creatures) like in the video below, though.
As you might imagine, the sex life of a small, immobile rock monster is appropriately weird. All of them are born as males, but when they reach puberty they become hermaphrodite. When it becomes time to get down to business, they spurt out a cloud of sperm and eggs into the surrounding water. But, if a Pyura chilensis is alone, it will procreate with itself through self-fertilization.
If the thought of this creature gets your tastebuds going, that fleshy red tissue is actually treated as a delicacy in parts of Chile, described to have a “slightly bitter, soapy taste.” Yum.
[H/T: The Verge]