Long before Marvel Studios and 'The Avengers' existed, Marvel Comics sold off the rights to many of its high profile characters to various studios. That's why Spider-Man can't meet Captain America and why the X-Men can't hang out with the Hulk -- Sony and Fox own the big screen rights to those characters and won't allow it. However, something peculiar is happening with the upcoming release of 'The Amazing Spider-Man 2': a post-credits scene that teases 'X-Men: Days of Future Past.'

Yes, a Sony Marvel superhero movie will feature a preview of a Fox Marvel superhero movie smack dab in the middle of the closing credits, with no real explanation. Specifically, it shows the scene glimpsed in the trailer where Mystique (Jennifer Lawrence), Havok (Lucas Till) and Toad (Evan Jonigkeit) battle William Stryker (Josh Helman) and a band of soldiers. The news comes via Empire, who confirm that the special preview is attached to British screenings of Spidey's new adventure [Ed. note: We have separately confirmed the scene has run in additional international territories where 'Amazing Spider-Man 2' has already opened]. We have reached out to Sony about whether or not American screenings will get the footage as well and will update accordingly.

[UPDATE: Sony has confirmed that the 'X-Men: Days of Future Past' post-credits scene will be included in the U.S. version of the film as well.]

This is a pretty big deal not only for the studios, but for fans who hope to one day see all of the denizens of the Marvel Universe hanging out on the big screen. If two massive corporations can realize that the same people are ultimately interested in both movies and can form a synergistic bond, then maybe it's not too crazy to imagine a future 'Avengers' sequel where Wolverine and Spider-Man show up to help kick butt and take names. Surely Marvel Studios can offer their rivals a few points on a massive team-up movie like that and everyone can walk away happy.

However, that's still a bit of a pipe dream. Sure, 'The Amazing Spider-Man 2' will tease 'X-Men: Days of Future Past,' but the footage is simply an excerpt from the finished film. It doesn't hint at connections between the franchises or promise a future team-up. Right now, it's just marketing instead of storytelling. But hey, it's a start.

[UPDATE #2: It's even more boring than marketing: it's contract negotiations. Variety reports that director Marc Webb owed Fox a movie from his old '500 Days of Summer' deal. Sony wanted him to direct 'Amazing Spider-Man 2' before he returned to Fox, and as part of that deal, Fox wanted a free plug at the end of the 'Spider-Man' sequel.]

'The Amazing Spider-Man 2' swings into theaters on May 6, 2014 and 'X-Men: Days of Future Past' arrives on May 23, 2014.