In homage to the classic Marvel series "What If?", this game has a "What If?" mode that can be accessed by the password screen, introduced by the Watcher (as the original comics were). With this mode on, you can play through the game and observe the (frequently hilarious) changes that have taken place. Changes range from insignificant alterations to complete deviations from the original premise. It is not present in the Nintendo 64 version.
Both Captain America and The Human Torch are voiced by Daran Norris. Both roles were also later played by actor Chris Evans.
When wearing the Spider-Man Unlimited costume (the one that gives the power of invisibility), Spider-Man can turn invisible during the bank levels and walk up to the robbers, listening to them exchanging small pieces of dialog with each other.
If the demo screen is left running long enough, Spider-Man will be seen through a gun barrel like the beginning of the James Bond films and fire impact webbing toward the screen.
When in "What If?" mode, if you let the game run without doing anything, Spider-Man will lie down and start to sleep. Sometimes he sings as well.