'X-Men: Apocalypse': Bryan Singer Shares Photo of Patrick Stewart on Set

X-Men: Days of Future Past Still James McAvoy Patrick Stewart - H 2014
<p>X-Men: Days of Future Past Still James McAvoy Patrick Stewart - H 2014</p>   |   Twentieth Century Fox
The director said his former star was just visiting the set of the upcoming film.

Let the conspiracy theories begin.

Director Bryan Singer has shared a photo on Instagram of Patrick Stewart visiting the set of X-Men: Apocalypse. Stewart, who has played Prof. Charles Xavier in four X-Men films, is not among the announced cast, and the actor has previously said he would not appear in the film. But this visit to the set will undoubtedly add to speculation that Apocalypse could involve a time travel element that could make including Stewart's older Prof. X possible. 

On Instagram Singer wrote Stewart was visiting and the director and actor were "reminiscing about our own #daysoffuturepast." Also pictured was another visitor: director Jason Reitman

Whether he pops up in Apocalypse or not, Stewart may not be done with the X-Men universe. In February, Stewart set the Internet ablaze by hinting that he might return for the third Wolverine film, which is set for a March 3, 2017 release.  

At Comic-Con earlier this month, Singer showed off footage from Apocalypse, which included plenty of Stewart's younger counterpart, played by James McAvoy — including the reveal of the young Prof. X rocking the bald-headed look the character is known for.

X-Men: Apocalypse is set for a May 27, 2016