Previously, Bryan Singer mentioned there might be a reference to Scarlet Witch in X-Men: Days Of Future Past as Evan Peters is playing Quicksilver.
There is even an official image still of Quicksilver with a younger girl, leading some to speculate that might be the Scarlet Witch.
Bryan Singer clarifies to Empire Magazine that the girl is not Scarlet Witch, but the younger sister, and at one time he intended on including a Scarlet Witch Easter Egg for fans, but ended up cutting it. In the comics, the younger sister to Quicksilver and Scarlet Witch is Lorna Dane, aka Polaris.
Is that the Scarlet Witch? No, that’s his little sister. I even had a line which I cut, where Quicksilver’s mother says to the little girl, ‘Go up and bug your sister,’ and the little girl says, ‘She bugs me!’ You never see the older sister, but it was to imply that there is an older sister for comic book fans. I ended up cutting it.
X-Men: Days of Future Past has a May 23, 2014 release date directed by Bryan Singer starring Jennifer Lawrence, James McAvoy, Michael Fassbender, Nicholas Hoult, Anna Paquin, Ellen Page, Shawn Ashmore, Lucas Till, Hugh Jackman reprising as Wolverine, returning cast members Patrick Stewart and Ian McKellan, with Peter Dinklage as Bolivar Trask.
The ultimate X-Men ensemble fights a war for the survival of the species across two time periods in X-MEN: DAYS OF FUTURE PAST. The beloved characters from the original “X-Men” film trilogy join forces with their younger selves from the past, “X-Men: First Class,” in order to change a major historical event and fight in an epic battle that could save our future.