"X-Men: Days of Future Past" director Bryan Singer has used Twitter as a promotional tool for the movie since the beginning of production, using the social networking platform to reveal behind-the-scenes production photos and tease new developments and characters. It's no surprise, then, that Singer hosted a 30-minute live question and answer session on Twitter in anticipation of today's "X-Men: Days of Future Past" trailer debut, where he answered questions from both Twitter and Facebook about coming back to the X-Men franchise, working with such a large cast, the characters he wanted to use in the film (but couldn't) and more.

Check out the highlights of Singer's Q&A below.

On the challenge of working with a larger cast:

.@lawrencer_ I was real comfortable with the original cast and knew the #FirstClass cast as a writer/producer but not yet as a director.- Bryan Singer (@BryanSinger) October 28, 2013

.@lawrencer_ With the exception of @NicholasHoult of course -- but they were all fantastic and made the experience fun.- Bryan Singer (@BryanSinger) October 28, 2013

On the funniest moment while shooting the film:

In between shooting a serious scene on Xavier's private jet, Michael, Nick, Hugh and James dancing to #BlurredLines #IHaveTheFootage- Bryan Singer (@BryanSinger) October 28, 2013

On whether "Days of Future Past" will echo '70s cinema:

.@TPF1138 Yes, in the colors, some of the style & music. I also used 16 & 8mm footage which I operated myself for some scenes which was fun.- Bryan Singer (@BryanSinger) October 28, 2013

On the development of Mystique between "X-Men: First Class" and "X-Men: Days of Future Past":

.@irturner She's a much more hardened kick-ass character than she was in #FirstClass.- Bryan Singer (@BryanSinger) October 28, 2013

On the overall tone of the film:

Although there is a great deal of humor, the overall tone is a bit darker than previous films, particularly because of the stakes.- Bryan Singer (@BryanSinger) October 28, 2013

On the new X-Men characters that appear in the film:

.@Jason_Payton82 A lot -- Blink, Bishop, Sunspot, Warpath, Ink, Quicksilver, etc.- Bryan Singer (@BryanSinger) October 28, 2013

On the characters he'd like to use in an "X-Men" film:

.@Bmike3030 Yeah, Gambit, Deadpool, and a few others I'd rather not mention.- Bryan Singer (@BryanSinger) October 28, 2013

On what brought him back to the X-Men franchise: