The 2-star level 201 Wolverine under the player’s control in the Here We Come node in Enemy of the State (intro mission before Hand Fortress) has an XP of undefined/undefined when you view his info.
Interesting exposal of underlying game implementation.
Means the devs are using a programming language that has explicit support for ‘undefined’ as a bottom value.
E.g. ECMAScript derivatives, such as Flash ActionScript or JavaScript.
Wasn’t the UI programmed with a ‘Flash-like’ toolkit & IDE?