Well, back to overanalyzing octo trailer
and the official Nintendo JP website.
First of all, because of tracksuit talk, what about the rest of Cuttlefish's outfit?
He has those distinct headphones, and his captain's hat is turned around. His shoes are pretty standard Splatoon slip-ons.
This guy will probably be involved.
He's the only passenger who didn't ignore the octoling, he's in focus on this promo, and he fits the rapper vibe. He's some isopod, so my first though is a connection to Sheldon. But his suitcase appears to be full of dolls and other toys(not seen: an octotrooper doll on the seat next to him).
So obviously this is the subway map, and the gear symbol must be options. But there's also a symbol that looks like an octopus with a thought bubble. Our own thoughts might be the new Sunken Scrolls.
The picture from the JP site also contains a message box. This is probably to contact Pearl and Marina, who, according to the wiki's translated info, are supporting from above-ground.
Apparently the green Octarians are "Sanitized Octarians." I was thinking clones, but this is much darker.
I can't tell if this is aboveground or very brightly-lit. It would be cool if we got other aboveground stops on the subway than just Inkopolis Square, even if we never get let out.
They've definitely gotten the aesthetic variety this time.
Since obviously the game was full of buildings floating in nothing already, they've really gone all-in with the surreal floating objects in these levels. Combine this with the level types we saw in the trailer, and there's a lot of stuff to be seen.