Oh, I’m sorry. If I ruined anything for people who didn’t know, you have my profound apologies. 
The identity of this has been finally revealed! It’s Pixar’s first TV special, “Reign of the Dinosaurs”!
But, John Lasseter said it would be the short in front of Toy Story 3.
Maybe both have to do with dinosaurs?
IncredigirlVirginia- The short in front of Toy Story 3 will be Night and Day, which doesn’t have anything to do with dinosaurs (though we thought that originally).
Thanks for the link, Bryko. I’m loving the sound of this! It’s so different to anything that Pixar has done before, but it’s a great direction for them to go in.