The design of Spider-Man's costume is based on the Spider-Man (2002) movie version with some additional inspiration from certain comic book art. The eyes move with expression similar to Steve Ditko's art, the webbing resembles the knotted spaghetti look that Todd McFarlane did, and Spidey has the has that gangly teenage look that Marc Bagley draws him with.
The show was originally conceived as an adaptation of the Ultimate Spider-Man comic book. However, plans for the show changed when Sam Raimi's Spider-Man (2002) movie proved to be a box office smash and Marvel crafted the series into a sequel TV series set during Peter Parker's college years to tide fans over until Spider-Man 2 (2004).
When Sony was working on the feature film Spider-Man (2002), Adelaide Productions got the contract at Sony to develop an animated TV series as well. Series director and co-executive producer Audu Paden, began working with one of the creative executives at Sony. At that point they brought in Brian Michael Bendis who did a pilot script for the series that was very edgy, different, and based on his Marvel comic book "Ultimate Spider-Man". With the Bendis script and some of the early conception art the creative team was working on, the show was shopped around. MTV thought it was great and in the fall of 2001 made a deal to bring the show to their network.
The show's animation was handled by Mainframe Entertainment and is done using 3D computer animation technology and techniques, and is rendered to look similar to traditional cel animation. According to a behind-the-scenes documentary on the DVD release, the plan was originally to animate the characters in traditional CG, similar to "ReBoot" and other series, but it was decided the characters would look more appealing if rendered in traditional 2D cell animation style.
After Adelaide Productions made the decision to make it a computer animated show, they needed to find out which studio could work with them on the show. Since Spider-Man is a popular character, a number of studios were interested in working on the project and open auditions were held. They wanted to know if the studio had the aesthetic and technical abilities to pull off what they wanted in their art direction. What they were looking for was this toon style line where the exterior perimeter of the character would have a line around it which storytellers could control very carefully. The studio that won the contract was Mainframe Entertainment, which works out of Vancouver, Canada.
Since the series was developed for MTV, stories were free of censorship marring kids programming. For the first time in a Spider-Man series characters were allowed to die on screen and there was some (mild) bad language.
A glitch in the computer animation led to changes in Mary Jane and Kraven from their comic book "look". MJ's long hair and Kraven's lion-mane vest tended to pass through their bodies, so animators went with a short 'do for her, and a leather jacket for him.
On this series, Harry Osborn has blonde hair, unlike the Spider-Man (2002) movie where he had brown hair or the comics where he had red hair. Photo of his father, Norman Osborn shows that he also had blonde hair as Harry and Norman have always shared the same type of hair.