You can have a poor drawing but the audience gets the joke – you have succeeded as a cartoonist. On the other hand if you have a technically perfect inked cartoon, but the gag is weak- it just a pretty drawing. Ouch!
The space cartoon get’s it funny punch line by give the reader some information that the character is unaware of. This makes the reader feeling a sense of superiority over the situation – understanding the “big picture”. So much for his fellow astronaut stuck outside!
