Back in 2012, a Comic-Con was held which previewed upcoming shows, information on them, and other things. I had a hard time finding info on it, but here's the only thing I could find relating to the promo and the event, a wiki which, seems kind of childish, but it's the best I could do to find evidence.
I watched the preview on YouTube some time ago, most likely from the same link the poster provided, but has since been removed, and since the clip shown under the promo has the "does not exist" error as well, it can be assumed that the YouTube User's account was deleted (most likely due to copyright).
This promo featured clips from the first group of episodes, memory serves up to Irrational Treasure, and a original clip of Double Dipper's cold open that was later changed (vocally).
This promo is available on YouTube, although admittedly in low quality.