Just about my favorite character from the Mysterious Benedict Society.
If you haven't read the series... DO. NOW. X3
In a nutshell, she's a 2-4 yr old (series takes place over a few years) who's INCREDIBLY smart and actually has psychic abilities. Also, she's a complete rebel and gets angry easily. (Somebody needs a nap...!)
This is how I always pictured her. Well, that, and the way she's illustrated on the covers.
Sticky Washington: [link]
Reynie Muldoon: [link]
Kate Wetherall: [link]