From left to right starting with the guy in the blue tie and ending with the guy in the violet tie: Frank Grimes, Callie Maggotbone (with Doug the Koala Man behind her), Mark Lilly, Randall Skeffington, Leonard Powers, and Twayne the Bone-Raper. Not pictured: Aldremach Maggotbone.
Bastard Boyfriend: To his college girlfriend, Jacqueline. The psychological damage he inflicted to her not only lowered her self esteem, but drove her to throw her life away so she'd one day become perfect for him.
Chick Magnet: Subverted. Kind of. We don't see Mark get as many girls as Randall or even Leonard, but the girls he does get are flat out gorgeous (Lilith, Callie, Jacqueline) They also seem to form an obsession with him.
Cultured Badass: His craftiness, quick wit and knowledge of how to behave in social situations gets him out of a lot of ugly situations.
Good Is Not Dumb: Some episodes show that he's a lot more on the ball than people think. Particularly the one where he's forced into selling his super-sized soul to Aldremach and gets it back by short-selling futures in the soul market, then spending the rest of the day debauching himself until his soul is the size of a pea. When Aldremach throws it out in disgust, he's able to get it back, along with 10 grand.
Guile Hero: Surprises you sometimes when he connives his way out of trouble.
Understanding Boyfriend: Most of the time with his girlfriends, the only exception being his girlfriend in college, who he coldly dumped while she was in the hospital because she was allergic to eggs. Eggs he forced her to eat.
A demon; Mark, Callie, and Leonard's superior at the DOI.
Black and Nerdy: Twayne fits this to a T, given his voice and some of the stuff that happens to him (e.g. getting a nosebleed while traveling down to Hell due to the change in altitude). One of the few characters to pull this andScary Black Man off simultaneously.
The Atoner: He never quite got over having accidentally killed his partner in his rookie days. Turns out he didn't really... and later in life he accidentally shot him again.
Character Development: In less than a season, he went from being an angry, frothing-at-the-mouth racist, violent cop to a mildly short-tempered clown who seems to berate the non-humans because he feels he's expected to.
Gag Penis: Grimes' wang is big enough to be used as a bludgeon.