Cybil, a white cat who has unique methods for getting Liō to feed her.

Fido, a spider who has helped him cheat on tests.

Quite often, father and son prove that they really love each other, no matter what. On the other hand, one day when the boy came home from school dejected because a drawing he created had horrified the faculty, Dad proudly hung up the piece of art on the refrigerator, giving his son much-needed comfort and joy (dated 5). When he watched a news report of an alien invasion, he gave Liō a spanking for apparently having piloted the alien ship and parking it in the backyard (dated at 9). He is frequently shown to be the subject of Liō's pranks, and sometimes he has to get his son out of difficult situations. In addition to Liō, the strip only has one other major character, Liō's unnamed father. Another recurring gag in the strip is parody of other famous comic strips, including Cathy, For Better or For Worse, Garfield, Zits, Calvin and Hobbes, Blondie, Peanuts, Pearls Before Swine, The Family Circus and Berkeley Breathed's strips. He is often seen using robots that he constructs himself for causing mischief. Some of the strip's recurring themes involve Liō getting even with grade-school bullies, helping animals (most of which are non-anthropomorphic but display obvious intelligence) defend themselves against humans or their predators, and performing mad scientist style experiments. Gags frequently involve the supernatural, alien invasion or mass destruction of many sorts, creating a surreal, disturbing atmosphere. The story is told visually, with little or no dialogue. The time period appears to be contemporary, except for an episode set in the year 2101, when Liō is in his nineties but still very much capable of mischief.

The setting of the story varies from Liō's house to his school and the general outside world. The strip focuses on the adventures of a creative little boy, Liō, who lives with his father (unnamed in the strip) and his pets.