Inkay and Malamar are based on cuttlefish, known for using brilliant displays of color to hypnotize prey and confuse predators (even though they are completely colorblind), as well as Vampire Squids, a type of squid incapable of the masterful changing of appearance to blend in most cephalopods are famous for, as they reside very far below the ocean with little light and little need to blend in, but are excellent users of bioluminescence to mimic what scant amounts of light reach the abyssal zone as well as buffet predators with a spout of glowing goo (as a normal squid would with ink, the black liquid is instead a bright color).
I like that Malamar has low Special Attack; if you go with the idea that Special Attack on Psychic-types represents their intelligence, then Malamar doesn't seem that bright - both cuttlefish and most squids, contrasting octopi, are not considered very intelligent.
Also, I like its focus with Topsy Turvy. A deep sea creature can only tell up and down based on the slight light from above, and using its bioluminescence to trick enemies into being able to have no idea what's up or down is pretty cool.
It's also a mindflayer cthulhu tentacle monster.
