I wasn't completely sure to rate this as "high" or "cosmetic" so to be on the safe side I put it on "high". I was playing Terraria mobile and running on a skybridge I had made. A wyvern attacked me, and I shot it with Tsunami using heart arrows. It acted normally at first, but when it became 'unfrozen' the entire body did not move at all, but the head segment detached from the body and moved independently. Only the head segment was seemingly capable of anything at all besides receiving damage.