Badass Bookworm: being an archeologist, he participated in dangerous mission in the past to save the extinct inhabitants of the planet, and lately, participated in the rebellion of his peoples against space invaders.
Cat Folk: kitten folk, to be precise. His race looks like one-eyed tailless kittens.
Color-Coded for Your Convenience, Red Eyes! Take Warning: In-universe. Their eyes grow yellow when then they become evil (orange for the really evil) and blue or gray when they become good. They even use this trait to determine prison terms - a criminal stays in prison until their eye grows green at least.
Mood Ring Eyes: Rrrr's race has eyes which change color depending on the personality - blue and gray for good ones, yellow for bad, orange for the worst.
Beware the Silly Ones: could be quite cunning and manipulative, usually for noble reasons (or at least reasons he considered noble). Several times sucsessfully manipulated his enemies into basically giving him the instruments of their defeat.
Космические пираты Крыс и Весельчак У (Space pirates Kryis (Rat) and Jolly U)
Befriending the Enemy: increasingly in later books, where they are both retired from actual piracy and became more like stolen merchants & illegal buisness patrons on the Pirate Planets. Consider their long conflict with Alice as some point of pride, and even help her on some occasions. Still pretty ready to do micheif on Galactic scale, albeit generally less cruel than before.
Cut Lex Luthor a Check: One of the books has the two in our time. Rat works as an actor double due to his power.
Enemy Mine: Used to be enemies before the police busted most of their operations. Their current alliance is built on nothing but convenience, and they state openly they'll betray each other without hesitation.
Even Evil Has Standards: increasingly in later books. In "The War Against Lilliputian", both show disdain toward Panchenga's criminal family, who profitered not only by piracy, but also from using captive childs as workforce, selling them into slavery, and, most importantly, doing this under the guise of a charitable foundation for an orphans.
In "A Planet for Tyrants", Kryis stated, that while they are willing to cooperate with a bunch of imprisoned tyrants, warlords & mass murderers to get their treasures (promised to pirates as the payment for helping tyrants escape from prison planet), they aren't mad enough, to actually let them loose in the Galaxy. Tyrants went furious, but pirates have guns.
Last of His Kind: Kryis is from a race that all but destroyed itself in constant warfare with each other. Partially averted, because his mother appeared in several books, and it was stated that some other members of his race still survived, hiding from each other in underground shelters.