I've had this idea that when Hum Drum grew up, he'd be similar to Batman; no powers, incredibly smart and strong, relies on his intelligence to defeat enemies, and a detective. I wanted his look to focus more on the detective aspect, but still wanted a cape; so coat-cape it is!
I went all out with the shading on this one, I attempted a background (but it didn't turn out so well, looked horrible and distracted from Sleuth here too much).
Super Sleuth is an amazing superhero, he's imposing when he enters a room, always seems to know exactly what to say and do, and puts civilians/other heroes/and even the villain's safety above all else. No one dies on his watch. His only downfall is that once you spend more than 5 minutes with him, his slightly scary, imposing stature, is suddenly destroyed by his complete dorkish nature. He snorts at terrible jokes, especially puns (also makes them at most inopportune times). Often trips on his cape if he's in a research frenzy (forgetting the outside world), and doesn't understand the concept of "Personal Space" (no one likes to turn around and find his gloomy scowl suddenly inches from their face).