I swear to you, I'm not making this up. The guys at ILM are known to do stuff like this.
Anyhow, I went to see Episode III again last week, and I noticed something out of place. During one of the Jedi Council scenes, I was looking at the crazy car thingies in the sky and, on a close-up shot of Ki-Adi-Mundi's face (for those of you who don't know, Ki-Adi-Mundi is the conehead one), you can see a SHARK in the background traffic! A SHARK!
...yup.
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Episode 2 has an x-wing chasing a TIE fight (or vice-versa) in the background of the car chase. Turn on the commentary on the DVD and it tells you when to look for it.