While Shailene Woodley was cast to play Mary Jane "MJ" Watson in 2014's The Amazing Spider-Man 2, the decision was ultimately made to omit the character from the movie. However, a blink-and-you'll-miss-it moment from the film's closing minutes seems to suggest that Woodley's MJ may have just barely made it into the final cut after all.
As the story goes, Woodley was cast to portray Mary Jane in director Marc Webb's Amazing Spider-Man sequel in late 2012. Apparently, the plan was for Woodley's MJ to play a minor role in The Amazing Spider-Man 2 before taking on a significantly larger role in The Amazing Spider-Man 3, the latter of which was never made. In mid-2013, however, it came to light that MJ had been cut from The Amazing Spider-Man 2 entirely. Sure enough, despite Woodley having filmed scenes as the character, Spidey's best-known love interest was nowhere to be seen when the film hit theaters the following year. Webb cited wanting to keep the focus on Peter Parker (Andrew Garfield) and Gwen Stacy's (Emma Stone) relationship as the reason for MJ's absence.
That said, the Wikipedia page for The Amazing Spider-Man 2 once had an interesting factoid: "[Woodley] can be briefly seen from the back during Rhino's attack at the end of the film." However, this claim was labeled with "citation needed" before eventually being removed from the article, warranting further investigation. Similar claims are made on other websites, including ComicBookMovie.com, Comic Vine and the Spider-Man Films Wiki.
While the deleted scenes featuring Woodley as Mary Jane were never officially released to the public, various photos and videos of Woodley on the film's set have surfaced online over the years. These leaks suggest numerous scenes involving MJ, including an encounter with Peter, as well as a separate encounter with Gwen. More relevant to the topic at hand, one particular batch of set photos suggests that The Amazing Spider-Man 2 would have involved Mary Jane working at a coffee shop. In these photos, Woodley is seen sporting a button-up denim shirt with her red hair braided.
The Amazing Spider-Man 2's final sequence sees Peter listening to the deceased Gwen's graduation speech from earlier in the film while the Rhino (Paul Giamatti) wreaks havoc on New York. And one shot, in particular, shows the occupants of a coffee shop reacting to the chaos going on outside. Behind the counter is a woman with braided red hair wearing what appears to be a button-up denim shirt. This very same shot can be seen clear as day in the official Amazing Spider-Man 2 trailer that aired during the Super Bowl in 2014. Not only that, but the trailer actually crops the scene to focus on the woman behind the counter, suggesting that she's of greater importance than some may initially realize.
In short, that little tidbit on Wikipedia actually appears accurate. While she's never named and her face is never visible, it looks like Mary Jane is technically in the movie, though Woodley remains uncredited. In all likelihood, the filmmakers saw no reason to cut a perfectly good shot, since fans weren't supposed to know that was MJ.
Still, the canonicity of MJ's involvement in the Amazing Spider-Man universe remains questionable at best. After all, Andrew Garfield's version of Peter Parker recently made his triumphant return in Marvel Studios' Spider-Man: No Way Home. In that film, Garfield's Peter tells his fellow Spider-Men of the night Gwen Stacy died, describing her as "my MJ." Shortly thereafter, Garfield's Peter confides in Tobey Maguire's version of the character that he doesn't have a significant other in his life, implying that he has yet to move on from Gwen. In other words, it seems as though Woodley's Mary Jane never showed up on Peter's doorstep informing him that he had "hit the jackpot" -- at least not yet.