The Tick is Really the Imagination of a Bed-Ridden Child
The main idea of this theory is that the superhero known as The Tick is really just an imaginary superhero that was made by a child on his sick bed. The theory also states that all the villains that the Tick had crossed paths with in the main series are actually based around inanimate objects. For example, the Tick's archenemy, Chairface Chippendale, is actually just an ordinary chair that was found in his room, and El Seed, a flower-based supervillain, is actually based on the flowers that could be found in his room.
The Tick's sidekick, Arthur, is actually the boy's father in real life. This is shown in the series in which Arthur is seen constantly moving because of his job as an accountant. The superheroine, the American Maid, would be the young boy's mother. This explains why the Tick never seems to be interested in her in the main series, despite her being blatantly sexualized.
The theory then ends with the idea that the young boy had contracted an illness from a tick, and this explains why he chose that name for his fictional persona.