Saw Avatar with OhOne last weekend. Awesome cinematography, cool effects, great work. A few random observations, with no particular theme in mind. Note that James Cameron says that "Avatar [is not] science fiction, it is an action/adventure/science fantasy film". So, I might just being too sciency here.
1. All of Pandora's animals are hexapods, except for the Na'vi which are quadrupod. The Na'vi don't even seem to have vestigial limbs. For a species that is supposed to be intimately connected with all life on the planet, they are seriously missing a Hox gene that everybody else seems to have.
2. What would be the fitness increase in having four eyes, paired in twos? Increased ability to gauge distances? Actually, that is kinda cool. Again, only the Na'vi don't have them. Did they also lose a copy of eyeless?
3. Hometree's central structure is DNA shaped, a sort of in-your-face symbolism. It's spiraling the wrong way though. Just saying.
4. What would cause the Hammerheads to invest so much in a bullet-proof armor? Also, with the high density the armor must have, and their body size that means a lot of calorie consumption just to be able just to carry your own weight.
5. Somehow, Ursula Le Guin's The Word for World is Forest is not mentioned as an influence to Avatar, but it certainly seems to be. Both have tropical rain forest worlds with sentient humanoid natives that are exploited by invading Terrans. The native humanoids have an intimate connection to the planet the Terran invaders do not appreciate and which ultimately cause their defeat. And yes, both stories are not-too-subtle contemporary political allegories.
6. I doubt a moon orbiting a gas giant would be able to sustain life, the orbit would be too erratic, tidal pulls would be too varied and strong, not to mention the climatic effects of prolonged planetary eclipses.
7. I want one of those AMP suits!