FUCKING NORMALSQUIDS
GET THE FUCK OFF MY STAGE

I'm fairly certain this might be part of the randomized graffiti system the game uses with Miiverse. I spotted a Pepe earlier on the mall map with the text "Meme Frog" next to it, and of course one of the top trending images right now is Miiverse graffiti of "Squidward Smells Good" (and there's another one in the gallery of "this is a load of barnacles").

It's pretty cool and I'm surprised I didn't know about this system prior to playing the game, as this really helps add to the "urban" feel.