These pics are all over the webiverse but still too good not to share (this amalgamation from Reddit)

Sea-urchins like to cover themselves with shells -perhaps for camouflage, perhaps for UV protection, perhaps to weight themselves down so they don't get washed away  ....or perhaps just for shits n grins.  Whatever the reason, some aquarists have been 3D-printing tiny headgear for their echinoderms, who were most receptive and joined the fashion show with gusto.  The story I first saw was from My Modern Met