The post-it notes in Peter’s apartment that you can see at the start of the game include a reminder to contact “T.S.” about a job and another to ask “R.R.” about a suit. These are most likely references to Tony Stark and Reed Richards, respectively.
The “Spider-Man P.I.” mission, in which you help a woman named Carmen, includes a heist room where you overhear characters named Niko and Deshaun talking, and they also mention someone named Roman. These names are all references to characters from Grand Theft Auto IV.
Just as he appeared in all Marvel movies, Spider-Man creator Stan Lee has a cameo in the game, appearing as a cook when Peter and MJ go out for dinner.
On the corner of Canal St. and Church St., you can find a movie marquee with the words “Maddie, will you marry me?” This was actually a real-life proposal attempt, put into the game at the request of a fan. Unfortunately, the relationship was not going well and ultimately didn’t work out. It’s possible that this proposal will eventually be removed from the game.
Many of the landmarks in the game are references to other characters in the Marvel universe. These include the Avengers Tower, the Sanctum Santorum used by Doctor Strange, Alias Investigations where Jessica Jones runs her detective agency, the Rand Corporation run by Iron Fist, and several more.
The trailers for Spider-Man have already included several Easter eggs. In the E3 2016 trailer, Spider-Man’s web shooter resembles that from Captain America: Civil War, a sign reading “Osborn for Mayor” suggests either Harry or Norman Osborn will appear, and we get to see the Daily Bugle newspaper.
A later trailer released in October 2017 includes a brief shot of the Sanctum Sanctorum, the residence of Doctor Strange.