And following is the code I'm currently using, but there must be a better way... right?
let first = &json["players"]["0"]["characters"];
if let Object(first) = first {
replay.characters[0] = Some(first.keys().nth(0).unwrap().to_string());
}
let second = &json["players"]["1"]["characters"];
if let Object(second) = second {
replay.characters[1] = Some(second.keys().nth(0).unwrap().to_string());
}
etc...