A phrase coined by the late 90's show, Kenan & Kel. "Aw, Here It Goes" is also the name of the shows theme song preformed by Coolio. The phrase is used when a person knows something bad is about to happen, or has just started to happen. Similarly, it can be used when someone comes up with a crazy idea.
Nickelodeon: "Let's cancel Kenan & Kel."
Everyone: "Aw here it goes!"