The series' main characters live in a blended family, a premise the creators considered underused in children's programming and which reflected Marsh's own upbringing. Marsh considers explaining the family background "not important to the kids' lives. They are a great blended family and that's all we need to know."[22] The choice of a platypus as the boys' pet was similarly inspired by media underuse, as well as to exploit the animal's striking appearance.[21] The platypus also gives them freedom to "make stuff up" since "no one knows very much about them."[22]
Marsh called the characters "cool, edgy and clever without [...] being mean-spirited." Animation director Rob Hughes is said to have noted that "in all the other shows every character is either stupid or a jerk, but there are no stupid characters or jerks in this one."[2]