1 Anakin: And another thing!
2 Anakin: If they're growing 10,000 worlds worth of food underground, you realise that means 10,000 layers of farms, under the entire planet?
3 Anakin: There isn't enough room in the crust for all that! The bottom layers would be magma!
4 Qui-Gon: Wake me when he's done and we've landed. I'll have Master Yoda kick his butt.
4 Anakin: And the oxygen...!

I'm sorry. I know this joke has worn so thin it needs to run around in the shower to get wet. I've finished now.

Unless I get another funny idea based on this. ;-)

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2013-03-02 Rerun commentary: Yeah, actually it doesn't quite mean that. They could have just converted all the rainforest and ocean into farms as well, which removes the need for about 9000 layers of farms. Leaving only about 1000 layers required.

Completely plausible now.