The Danza: The Seiyuu Kana Nanba is played by Kana Asumi. The anime director Masaki Ehara is played by Masashi Ebara. Both cases seem to be intentional, as both characters are renamed after their seiyuus. In the original manga, Kana Nanba's name is Kanra Natara, and Masaki Ehara is just named Ehara.
The special chapter based on Hiramaru's Otters 11 manga features Otter 11 stuck in a job he hates and working with a man named Yoshida, whom he gets along with poorly.
Shiratori, one of the main characters' assistants, doesn't seem to get along well with the rest of his family (with the exception of the dogs), who don't think much of his being a manga assistant. He writes a story about a boy who's lost faith in humanity, but has a dog companion who senses people's feelings.
Nobuhiro designed a character from Superhero Legend, "Torishi-man" after Torishima, the same way Akira Toriyama based Dr. Slump 's Dr. Mashirito on him (as Takagi notices).