Gravity Falls (found Comic Con 2012 promo of Disney Channel animated mystery comedy series; 2012)
From The Lost Media Wiki
In 2012, a Comic Con was held which previewed upcoming shows, information on them, and other things. It is difficult to find info on it, but a blog relating to the promo and the event, can be found here.
The preview was 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).