Last month, we reported that Bryan Singer has signed on to direct X-Men: Days of Future Past, after Matthew Vaughn dropped out. Today, the filmmaker dropped a bombshell on his Twitter account, confirming that X-Men stars Patrick Stewart and Ian McKellen are returning as Professor X and Magneto in X-Men: Days of Future Past. He also confirmed that James McAvoy, Michael Fassbender, Jennifer Lawrence, and Nicholas Hoult are returning.

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Naturally, this revelation poses many questions, such as how will the older Professor X and Magneto exist alongside the younger versions played by James McAvoy and Michael Fassbender? Here's what Bryan Singer said, when asked that very question.

"The movie is called X-Men: Days of Future Past, use your imagination. More to come."

We reported earlier this month that production will begin on X-Men: Days of Future Past in April 2013.