Quote Originally Posted by Anteros View Post
I'm sure you're right about Jean, but I've apparently missed the stories when she acts like that. I know that the young Jean they had running around for a while was a jerk, but I feel like that's basically an entirely different character.
Canonically they're not.

They are conically the same Jean--adult Jean eventually inherited Teen Jean's memories after Teen Jean when back in time and buried her own memories and those of the other O-5 to maintain the timeline.

Though as far as I know, the worst thing Teen Jean did was out Iceman after reading his mind and finding out he was gay. Adult Iceman eventually called out Adult Jean on how much of a **** move that was after their teen selves went back in time to become their adult selves.