Update: Summarized the original, nuked, writeup.
Captain Planet and the Planeteers was a cheesy, frighteningly PC cartoon show in the early 90s. There were five kids from all over the world, each with a ring that allowed them to use a specific power: Fire, Water, Earth, Air, and Heart. Now, when Casting the Circle, Wiccans invoke the four elements (Fire, Water, Earth, and Air). Now, if you come up with an explanation for Heart as just an addition to allow them to wedge a cast member of another culture in there, it sounds as if the show is promoting Wicca. This could be (and undoubtedly is) construed as part of the "Vast Pagan Conspiracy" (a subset of the Vast Left-Wing Conspiracy). A cartoon show — what could be more insidious?
Of course, it doesn't hold water on further inspection. First off, the four elements relate back to alchemy. Wiccans actually lean towards a five-element view; the fifth isn't "Heart" (Love) from the show, but rather Spirit, assigned to the top point of an upright pentacle.
In addition, Gaia was depicted as kind and compassionate. While some fluffy bunny types might agree, in general practicioners of Wicca realize that sometimes Mother Nature is a bitch. To go further, one might construe Gaia and Captain Planet as a God and Goddess duo, but they both seem rather neuter — Gaia seemed to be leaning towards cronehood, while the Captain looked teenaged.
Furthermore, many Wiccans feel the Wiccan Rede takes a dim view of violence used to further one's ends, no matter how good for the planet the ends might be.
(Personal opinion: The show sucked, being at best an example of wish fulfillment and "corporations are evil")