The Captain is actually the original playable character from Splatoon for the Wii U.
Craig Cuttlefish is the original commander of the Squid Beak Splatoon before he retired.
Callie (agent 1) and Marie (agent 2) are a group of pop stars named "the squid sisters"
The salmonids in the mode salmon run pride themselves in being eaten and tasting good it is also known that inklings eat salmonids because in mako mart a stage that came back from splatoon 2, it is shown that the store sells salmon meat also in the Grizz co in grizz co in the freezer that there is salmonid meat packaged.
Unlike the previous game, playable Octolings are unlocked from the very start, instead of requiring DLC to obtain.