"X-Men: Days of Future Past" writer Simon Kinberg talked about the controversy surrounding the addition of Quicksilver to the cast.

In an interview with Total Film, Kinberg explained the production was unaware "Avengers: Age of Ultron" would be adding in Quicksilver to their film. FOX holds the "X-Men" rights while Disney holds the rights to Marvel's "Avengers."

"It wasn't something we anticipated because we didn't know they were using him in the 'Avengers' movie. We only found that out...weeks after we made the decision that we had done it. And then, after that even, I think it was a little while before the controversy started," Kinberg told Total Film.

Kinberg added that they were also toying with the idea to adding in Scarlet Witch to the franchise, but the scene was cut from the film.

"We talked about bringing Scarlet Witch into the mix for this film," Kinberg explained. "Actually, there was a little scene that we shot that we ended up cutting out of the movie that eluded to her. It was sort of an interstitial scene that didn't push the movie forward and so it ended up being cut..."

Kinberg also confirms the appearance of Quicksilver, played by Evan Peters, in the next "X-Men" installment. You can watch Kinberg's interview in the video below.

In other "X-Men" news, director Bryan Singer recently admitted to SciFiNow he hopes fans will overlook continuity errors throughout the film.

"Some things you let go. In X-Men 3 Bolivar Trask was an African-American guy, in X-Men 1 I personally wrote the line that of course I now regret: 'When I was 17, I met a young man named Erik Lensherr' and then in X-Men: First Class I changed that!" Singer told SciFiNow.

"Some of these I hope the audience will forget about but for the bulk of it I pay attention to the universe," he added later in the interview.. "Not just X-Men 1 and 2, but also X-Men 3 - I was thrilled to have [Kitty Pryde star] Ellen Page in the movie as character - and even The Wolverine, I try to look at all those. In fact [writer/producer] Simon Kinberg and I wrote a little scene for the end of Wolverine which James Mangold directed and put at the end of The Wolverine just to reintroduce Patrick Stewart into the universe, so there's some benefit to it as well."

"X-Men: Days of Future Past" will be released to theaters on May 27.