It is often used as a catchphrase when someone thinks about a new theory about the end of the comic.
The alt-text has since changed; see alt-text.
Throughout the exposition of Time, "Wait for it" was interpreted in several different ways.
The phrase could be a command telling the reader what he or she must do to experience the comic. The reader must wait for the newpix to come. Without this, a person may glance at the comic, think it to be a nice beach, walking, wildlife, or waterfall scene, and move on without realizing that the image changes.
Meaning of the Title
"Wait for it" could suggest an interpretation of "Time," the title of the OTC, such as that the only thing you can do about the movement of time is wait for it. Or, that if you wait long enough, time will come.
"Wait for it" is a common phrase that, when on it's own, is usually used to signal that something momentous is about to occur. This builds suspense, and heightens the meaning of the anticipated event.