How to Be an Anorac

Anorac is a word used to describe people who have intense levels of expertise or interest in something. So for example, they've said Thomas is such an anorac when it comes to train trivia. My main anorac sort of area would be the Beatles, of course. We also have the expression shotgun as well - if you're driving somewhere with some friends and you want the front, the passenger seat in the front, you would have to say shotgun. And if you say shotgun, you get the passenger seat. Do you have a similar word in your language where it's like you use it to claim something? Bagsy the front seat. Dibs is the same