In one of my novels, the one I'm currently focusing on, I decided to give the protagonist, a teenage girl, a sidekick throughout her adventure. My original idea was to make him an Amy Adams fan (because I am too), but after arguing with a friend of mine, realized that this was more of a personal in-joke than a true kicking-off point for humor. So I decided instead, again drawing on my real life obsessions, to make him an Indiana Jones fanatic. As in, he actually goes around dressed as the character. No, really. I actually used to do that, that's how weird I was. I just thought it would be amusing to have a character that interested in something, especially since said thing is something I love as well. I think it's a fun and interesting personality quirk, and something that hasn't often been touched upon (the Indy fandom, I mean. Usually it's Star Wars fans or Trekkers). Does this character sound endearing or interesting at all to you? The primary reason for establishing this obsession is because at some point later in the story, our heroes encounter booby traps, and the character, being the super-knowledgeable fan he is, is an expert at evading traps, so it actually pays off and ends up being hugely important, not just a random quirk.