I'm not entirely sure as I haven't read it in detail, but generally it might be about the adventures of a hobo who has a shotgun. It could involve his struggles, the things he encounters while wandering around with his trusty shotgun.
Sure. There was a hobo who found an old guitar on the street. He started playing it and his music was so strange yet funny that it attracted a bunch of pigeons which started dancing around him as if they were his audience.
It's possible that the main character is an underdog. Hobo Johnson might have created a character who is facing difficulties but has some kind of charm or tenacity that makes the reader or listener root for them throughout the 'best story'.
The main character is most likely the hobo with the shotgun. There might also be other characters like the people he meets on his journey, perhaps some villains he has to deal with or even some fellow hobos.
A hobo once found a pair of roller skates. He put them on and tried to skate through the park. He was so clumsy that he ended up crashing into a bush, but instead of being embarrassed, he started laughing and told everyone that it was part of his new 'comedy act'. He then entertained the park - goers with his made - up stories about his adventures on wheels.
One railroad hobo horror story is about a hobo who entered an abandoned train car at night. As he was settling down, he heard strange scratching noises coming from under the floorboards. He thought it might be rats at first, but then the scratching got louder and more violent. He felt as if something was trying to break through. Terrified, he ran out of the car and never looked back.