Hello
This is Bloo(Blooregard Q. Kazoo) from Fosters Home For Imaginary Friends! I spent a lot of time making his mouth(you won't believe how difficult it was to make it like Bloo's   )
So I hope you like him and also you can give some ideas!
I will try to make the other friends too so stay tuned  

About the mouth, what about a small path, stroke it and you're done? Perhaps put a Gaussian Blur on it to make the pencil (you'll probably use pencil for this path) look less hard. For the result, it is alright, but could be made a bit more interesting. Some glass effects on the character?

Yes I thought about a glass effect but if you look at the real character...well it doesn't need any glass effect but I will try to play with it