It's hopeless as a secret. Also (characterizing something as a secret is) like daring them to get it. The point is protecting people's enjoyment of the film. the movie will be successful if both those who have been fans of the material appreciate it, have fun with this, walk out and talk about it, but also those who have never seen a Batman movie, a Superman movie, a Wonder Woman TV show, they decide to come take a look and they are also won over and moved by it.