You can find these things clinging to the walls, ceilings, and floors of the Deepsea Metro subway trains. We’re not sure if they’re paying customers or what… And how do they get on and off the train?
— Squid Research Lab
Source: Splatoon’s Tumblr.
…Wanna play? Buy a Switch.
And if you’ve already got yours, click on Splatoon 2 for everything you need to know about the game. 😀