Fox and Marvel have a long history of not getting along. Both studios have had this spot for more than a decade Kevin Feige has talked in the past about how he has extended a hand to Fox for a collaboration between the two studios, but Fox has not replied to his offer. So it may be surprising to read that they have actually collaborated (sort of) for their films Deadpool and Guardians Of The Galaxy: Vol 2.
Deadpool writers Rhett Reese and Paul Wernick revealed that they wanted to change all the characteristics including the abilities of Negasonic Teenage Warhead besides her name. For this to happen, they needed a special permission from Marvel Studios (The X-Men are Marvel characters).
Marvel Studios gave their permission but with a condition. Marvel wanted to exchange Negasonic Teenage warhead with Ego the Living Planet for Guardians Of The Galaxy: Vol 2. Both studios agreed to the exchange and left with what they wanted.
“Kurt Russell [Ego the Living Planet] in the new Guardians movie was the character that Fox swapped with Marvel to [change] Negasonic Teenage Warhead powers.”
In the comics, Negasonic Teenage Warhead was a mutant who had telepathic and precognitive powers. The movie version or the altered version was able to emit a “telekinetic detonation” around herself, making a literal power that matches her name.
Since Ego the living Planet is actually a Marvel character, you would think that the studio would not have to get an exchange for him. But given that he is associated with the Fantastic Four and the X-Men, it was just a chance that Marvel was not willing to take.
Since Ego The Living Planet is playing a major role in the Guardians Of The Galaxy 2, it seems like Marvel got the better end of the stick in this situation for now. With Deadpool 2 in pre-production, we may also get more time with the teenage mutant in the new film.