The Na'vi are non-mammals who have no use for nipples to breastfeed, let alone the perfect digitally rendered boobs sported by Neytiri, Zoe Saldana's character. So why do the Na'vi, who don't even need genitals, have breasts?

A straight-faced James Lipton posed this question to James Cameron while taping an upcoming episode of 'Inside the Actors Studio' a source told Uinterview.com.

Once the audience's laughter subsided, Cameron paused from laughing and responded, "Because this is a movie for human people." The crowd roared again. Cameron went on to explain further his philosophy of the Navi character design. He boiled it down to: "Let's focus on things that can create otherness that are not off-putting."

This is not the first time that Cameron has discussed his characters' nonfunctional sexual attributes.

"Right from the beginning I said, 'She's got to have tits,' even though that makes no sense because her race, the Na'vi, aren't placental mammals," he told Playboy magazine.

As much thought as Cameron put into creating perfect breasts for his heroine, her nipples had to remained covered by a strategically placed necklace because of the movie's PG-13 rating.

A Na'vi sex scene, complete with trembling "queues," was deleted from the final cut of the movie, but it will be included in the DVD. Zoe Saldana described Na'vi sex like this:

If you sync to your banshee and you're syncing to a tree, why not sync into a person? I almost feel like you'll have the most amazing orgasm, I guess.