Go to Special / Cheats and enter the codes from the list.

Code             Result

FUNKYTWN         Toon Spidey  
STICKMAN         Stick Spidey  
CLUBNOIR         Ben Reilly Costume  
ADMNTIUM         Invulnerable  
UATUSEES         What If Contest  
RGSGLLRY         Character Viewer  
CINEMA           Movie Viewer  
FANBOY           Comic Collection  
MME WEB          Level Select  
KIRBYFAN         Game Comic Covers  
ROBRTSON         Storyboard Viewer  
SM LVIII         Quick Change Costume  
MRWATSON         Peter Parker Costume  
KICK ME          Amazing Bag Man Costume  
XILRTRNS         Scarlet Spider Costume  
SYNOPTIC         Spidey Unlimited Costume  
TRISNTNL         Captain Universe Costume  
MIGUELOH         Spidey 2099 costume  
SECRTWAR         Symbiote spidey costume  
RULUR            J James Jewett  
EGOTRIP          Pulsating head  
GLANDS           Unlimited webbing  
LEANEST          Everything  
WEAKNESS         Full health 

Thanks to Revolution reader!