What is it?
A gag cover was a cover where something shocking and seemly out of the ordinary (usually a character such as Superman acting grossly out of character), so the fans will buy it. Usually, this is just a scene taken out of context. For example, a cover may have Superman destroying a car and inside it turned out the car belonged to criminals. However, sometimes the cover completely lied. For example, the cover of Superman # 293 shows Superman refusing water to people dying of thirst despite the actual story is about the people becoming avert to water and Superman has to find away to get them to drink it.