Graffiti is found all over Inkopolis, from every stage to the Plaza and Square. While there are many forms of pre-made graffiti for these cases, like stickers and scribbles on the ground, and on billboards and on walls, it is also shown in the form of player drawings. During Splatfests, these can be seen on the back of the two trucks Callie and Marie dance on top of in Splatoon, as well as on banners, neon signs, and in the sky as fireworks.
Some, if not all, graffiti in Inkopolis Plaza is implied to be made by jellyfish; as stated in a developers' interview, jellyfish are known to create a large amount of graffiti.[2]
Some of the stickers are Easter eggs which depict other Nintendo characters, such as Bloopers or Octoroks.
Miiverse or in-game posts can be hidden via the Options screen. They will then be replaced by Splatoon-related placeholder drawings, the source of which is unknown, but can be assumed to be made by the developers.
If a player holds down when in the Plaza or Square while aiming at drawing made by players, they can "yeah" or "fresh" it.
The background color of the player drawings in stages is the neutral color of the two ink colors in the current battle.
For the nametag graffiti stickers, there are different variants appearing in Octo Valley and Octo Canyon compared to those found in Inkopolis. In the Octo Expansion, round versions of the nametag graffiti stickers can be found.