15X-Men - Spider-Man Steals The Scene
This first entry is less of a serious effort from the filmmakers, and more of a prank on the cast. It's also a great treat for any fan dedicated enough to comb through the X-Men DVD extras, as it appears as a blooper in the movie's first edition.
In the clip, we can
see Spider-Man climb up and out a window to sneak up behind Cyclops, Jean Grey, and Storm as they down a hallway. The actors are clearly surprised as Spider-Man bashfully declares he's in the wrong movie. He's subsequently chased out of the scene by James Marsden, who plays Cyclops.
The man behind the mask in this cameo is Scott Leva, who was actually intended to play the role before Tobey Maguire, when Cannon Films first procured the rights in the 1980s. Leva was a stunt man working on X-Men, and it was director/writer Bryan Singer's idea to execute the gag.