Starfish are bizarre. They start as a bilaterally symmetrical larva, then grow a stalk that attaches to the sea bed. They grow, then rearrange themselves into a pentaradially symmetrical form.
Oh, geez, that reminds me of the Mimics from All You Need Is Kill (the basis of Edge of Tomorrow. In the novel, the Mimics are not the alien invaders themselves, but rather nanomachine colonies sent by the actual aliens that infest and control the bodies of starfish, adapting them to combat use.
https://en.wikipedia.org/wiki/Starfish
Plus they can regenerate from a severed limb! Creepy, but very interesting too.