A TV "hero" who was summoned by a group of "planeteers" to defeat "eco-villans". The summon starts with "Fire" and continues with the rest of the planeteers with "Earth", "Wind", "Water", and "Heart". This, in turn, summons Captain Planet to save the day in this fictional TV show.
Also, it's a general internet fad for GameFAQs
message boards, wherein each user starts the fad with "Fire", and the rest of the people are expected to follow through with the summon until the original "Fire" poster or sometimes another poster finishes the summon. These summons, when pulled off correctly are usually found funny, and make any topic off-topic and marked for deletion. Anyone who breaks said fad, is dispised.