After watching a movie your first impression of it was that it was mediocre at best, yet after a few hours or days have gone by, the movie keeps popping in and out of you thoughts. So, at the time of watching the movie you had no idea it would have such a profound effect on you and yet now its all you can think about. It crept up on you so to speak.
Mike: Dude, I just saw Adventureland last night, and I didn't think much of it at the time, but now its realistic portrayal of teenage life suddenly seems so much more relevant.
Joey: Dude, you just saw a Sleeper Movie!!