The selective deficit in generating human figure representations always derives from limited practice in drawing.
How to sketch ?
The world is full of unfinished drawings. Most of the fun of drawing from life is that you can exagerate. Don't be afraid to be imaginative. Your life model model also provides a handy set of "rules of thumb" for selecting specific whimsical images for various applications in the online (humorous) art site.
The arts matter because they deal with daily experiences in a transforming way; because they take us out of ourselves; because they encourage the imagination; because they offer a shared experience rather than an isolated one.