Splatoon seems to be developing quite the fan art following already....

I heard that the game director stated that the Inklings don't actually notice that Marina is an Octoling, they only care that she's fresh.
some marina info from that interview

The interviewer asked if Marina is an Octoling, but they all dodged the question and Nogami simply said, “She has extraordinary hair”. Nogami also noted that Inklings are not paying attention to this too much. Inoue said that the Inklings don’t care about appearances if they are doing something fresh.

The Squid Sisters had composers who produced their songs. However, Off the Hook are composing their music by themselves. Because of this, Inoue designed them to represent self confidence.

Pearl is genius artist, but she couldn’t find a right partner because she’s a bit too edgey. Since she finally has Marina as a partner though, their chemistry is sparkling right now.