The term "Sleeper Curve" was coined by Steven Johnson, which he derived from the Woody Allen film Sleeper. Johnson's book Everything Bad Is Good For You is where he invented the phrase.
The film is about a cryogenically frozen young man who wakes up 200 years later in the year 2173. In this futuristic society, they've lost a lot of knowledge about American history due to an aggressive, police state that America now is. When talking to this man, scientists are baffled to learn about their countries past and what they considered to be good science. One specific idea they couldn't grasp was that twentieth-century society failed to grasp the nutritional benefits of junk foods such as hot fudge.
What Steven Johnson says is that any subject can fall under the sleeper curve. Anything that has to slowly gain popularity and acceptance would be considered something under the sleeper curve. For today's standards, pop culture has a negative connotation associated with it. Maybe someday society will realize the positive benefits of video games and television shows.
Johnson claims that pop culture has grown to be very complex, intellectually challenging, and cognitively demanding. He claims that television can determine how well we comprehend interpersonal relationships, and it represents real life social network maps via reality television. As for video games, he says they are a new way of cognitive exploration and brain stimulation.
To sum things up, an idea or subject that falls under the sleeper curve would be something that society as a whole has been oblivious to or "sleeping" on for quite some time. While a topic now may be taboo in today's society, it may become more accepted in the future.