The Annoying Orange lost episode. "???" is not a placeholder, but was the title of the episode itself. 2011 is the assumed release date of the video, which most people recollect lasting about three minutes in length. The episode is sometimes also called "The Secret Episode", though it was not released or hyped up with significant fanfare. It was the Secret Episode as this was allegedly the running joke throughout the otherwise normal episode. It's disappearance and lack of resurfacing may also be an extended commitment to this bit on the part of the creators, or it may have been a ruse created to sell the legitimacy of why this episode is unfound.
The Annoying Orange tells Apple to watch out for a secret. But when Apple asks him what he's watching out for, and asks if it's a knife, he gets told "Shhh! It's a secret! It's the Secret Episode, Apple!"
Many other characters are "Shh'd!" by Orange throughout the runtime.
At the end, Apple gets hit by the knife anyway.