Well, it could be in some very specific types of fictional or perhaps satirical literature. But it's not a mainstream or common description in general literature. It might be more likely to be found in some over - the - top or niche fictional works.
The origin of the phrase 'gargantuan busty mother' in literature is not easy to determine. It could be from some local or regional writing that has not gained much popularity on a large scale. Maybe it was created by an unknown writer in a small community who was using it to create a very distinct character in their story. Or it could be from some early form of subversive or underground writing that was meant to shock or amuse a small group of readers, but over time it might have been forgotten or only known in very specific circles.
The dog might bark at the mailman in the cartoon because it's instinctively wary of strangers. Or maybe the dog is excited and just expressing itself in a way that seems like barking at the mailman.
To draw a cartoon stargirl, begin by drawing a circular head and then add cute features like a button nose and a small mouth. For the body, make it slender and give her a flowing dress. Add stars on her dress and in her hair. Shade it lightly to give it a 3D effect.
You might try local comic book stores in the Denver area. Some popular ones include XYZ Comics and ABC Collectibles. They might have what you're looking for.