Continuity mistake: When Kath, Garry, Kim and Sharon are on the tram, Kath sends Kel a message and sends an attached picture, which Gary ruins. Later, when Kel receives it the photo is different, because now Kath has a surprised look on her face. She didn't appear that way before.
Factual error: In 4.2, "Fame," Prue and Trude see Kath and Kel arrive at the awards, and act surprised they are together. However Prue and Trude have seen Kath and Kel together at their shop several times and laughed at their dress sense, etc. They also didn't know who Kel was before, and in this episode they do know his name.