Familiarity with natural anatomy, coming from consistent observation and sketchbook practice, enables the artist to enrich their work with dynamic form and communicate ideas more clearly.
Building upon this foundation, the development of characters proceeds.
In much the same way that we exaggerate details from our experiences to add humor or push a story, occasionally resulting in the "tall tale", we exaggerate our physiological form and movement to create interesting characters. Paul Bunyan, the legendary giant lumberjack, may be based on an actual person who lived long ago. This person may have been the biggest person around. Perhaps he was 6' 8" and 250lbs, within the realm of reality but why not, in the story, make him fifty feet tall!?
Illustrate a story of your favorite pillow fight from when you were a kid but add exaggeration: draw lots of feathers sticking out of you and your friends' hair. Add an image of someone lying beneath a pillow with their feet up in the air and, off to the side, a broken lamp.
Observe an elderly man in the park, feeding pigeons, as another hypothetical example. Draw him, observing how he moves in space and how the folds of his clothes operate, how weathered and wrinkled his face is, how the birds react to the move of his arm.
OR, draw him being carried off by a bunch of these birds,...
...while a young child silently watches, surprised. The caption should read: "We're out of peanuts! Just making a run to the store!".
Can't come up with a character out of your head? Chop up pictures of people from magazines, separating their torsos, heads, legs, feet, etc. and toss it all up in the air. Assemble random parts together, like Frankenstein, taping them together on the back. Now trace this being with tracing paper and a pencil, or otherwise develop them.
Give them a name.