Let me show you how to draw funny cartoon faces by changing only a couple of elements in the faces of your characters. It's not difficult to create something weird or original, but is it really funny?
In the first three examples, I have only changed the eyes of the character from one drawing to another. Nothing too fancy, nothing too exaggerated. It does look funny, but it's easy to do something more effective!
In the next three sketches, only the mouth was modified. Once again, it's enough to create funny faces, but it's not what I'm looking for.
To make things more interesting, I have created three heads with misc shapes. Combined with funny mouths and strange eyes, these three characters are already funnier than the six displayed above.
These characters are similar to the ones available in the previous step. However, their eyes or mouth are longer and larger giving each character a very strange look. Unlike the previous faces, these expressions are virtually impossible to reproduce in real life!
That's what I call an extreme example! So it's really up to you to choose how to want to manipulate your character in order to make him funny. Too much it's not necessarily funny. You just need to play with the right parts in order to create something fun and original! Enjoy!