Come up with an idea for a crazy cartoon character, it could be original or it could be borrowed.
Think about how you can make it more interesting.
Lightly draw it out on paper, and then darken (or trace in pen) the lines you want to keep and erase the ones you don't.
Colour and shade with pencil crayon or markers.
The girl with the hat is my daughter drawn as a cartoon. The little green guy is in the back of my Ipad case.
Calvin and Hobbes done up like Doctor Who.
Seasame Street characters done up like Batman characters.