Concept art (Special Edition version)
Select the "Art Gallery" option at the special features screen. Highlight the "Main Menu" option at the next screen, then press Up to highlight Wolverine's dog tags. Press Enter to view concept art for The Beast and The Blob, which were characters that were cut from the production.

Spider-Man (Special Edition version)
Select the "Trailers And TV Spots" option at the main menu. Press Left to highlight the rose in the top left corner of the screen and press Enter to display a hidden screen featuring Spider-Man.