'X2' Originally Featured Jean Grey's Full-Fledged Transformation Into Phoenix

X2: X-Men United was originally planned to involve Jean Grey's full-fledged transformation into Phoenix, but screenwriter Zak Penn tells The Hollywood Reporter it was "too soon" to tackle one of the X-Men's most famous comic book plots in their second movie.

"On X2, part of how I ended up getting the job on it was that originally that was going to be the Phoenix story," said Penn, who convinced director Bryan Singer to hold off. "I just said ... 'You've built up this real universe and you should establish it more before you go into Phoenix.'"

Penn exited the project before shooting, ultimately receiving a story credit on X2.

"It was too soon to go into the Phoenix story and it was too soon to get cosmic. I would say that's probably the biggest contribution I made... pushing it in that direction," Penn said. "There are a bunch of scenes I wrote that are still in there. I don't remember what movie I left to do while they were making X-Men 2, but that was kind of the story of my life. I would come in and do something and then leave."

The 2003 X-Men sequel ended with the telepathic mutant (played by Famke Janssen) heroically sacrificing herself for her teammates with the help of a newly unleashed power.

Just before its end credits, a sweeping shot reveals a soaring, bird-like shape reflected in water with a fiery glow — signaling the birth of the Phoenix — who would menace the super team as a villain in 2006's X-Men: The Last Stand, co-scripted by Penn and series regular Simon Kinberg.

The oft-maligned The Last Stand partially adapted the Dark Phoenix Saga, the famous 1980 comic book storyline from Chris Claremont and John Byrne, but the threequel was ultimately poorly received by fans and critics alike.

X-Men: Dark Phoenix, part of Fox's quasi-reboot depicting a team of younger X-Men, will adapt the story for the big screen a second time.

In this iteration it will be a teenage Jean Grey (Sophie Turner) serving as the vessel for the unwieldy powerful force, which she was shown to possess in 2016's X-Men: Apocalypse.

Earlier this week, Dark Phoenix was pushed back from its planned November 2018 release to February 2019. Comicbook.com learned "significant reshoots" are responsible for the delay.

Penn's latest, Steven Spielberg's Ready Player One, is now playing. X-Men: Dark Phoenix opens February 14, 2019.