Spider-Man: No Way Home featured the return of several familiar villains (and a couple of heroes) from alternate realities, but it looks like there were originally plans in place for another character to make her MCU debut as a result of Doctor Strange's spell.
Some official No Way Home concept designs have been shared online by artists Maciej Kuciara and Marek Okon, and they confirm the rumor that America Chavez was going to be introduced in the Sony Pictures threequel.
The first image shows Chavez standing in the middle of what looks like a bumper car rink holding a mysterious book while Peter Parker, MJ, Ned Leeds, Flash Thompson and Betty Brant look on. The second appears to reveal that the Multiverse-traversing hero was going to play a part in the final battle (is she holding the Green Goblin cure here?)
Xochitl Gomez will play Chavez in Doctor Strange in the Multiverse of Madness, but based on this artwork, it looks like Isabela Merced (Dora and the Lost City of Gold) was being considered for the role at one point.
Saving Chavez's debut for the Doctor Strange sequel was probably a wise move, but remember, Marvel Studios was originally going to release In The Multiverse of Madness before No Way Home, so audiences would have been familiar with the character when she showed up to lend the wall-crawler a hend.