They were all great, but the first ones we made were fire based lifeforms living on the hot side of a tidally locked planet with no other traces of life. They aren't individuals as we'd understand them, but can detach and exchange the components that make up their selves. This is done to transfer information or even fuse together several beings when a task requires it.
When advanced humans made first contact by landing in heat resistant suits, the fire beings thought these lifeforms must be like them, and suggested in their language of colours to exchange personality parts with the new arrivals. The humans recorded and played back the same colour signals, not understanding the language, and the fire beings took that as agreement and crowded in, overloading their suits and killing the landing party.