Dirty Zerby

Walter the wash truck is washing down the Zerbies who are all having fun playing in the mud. When he washes Lily, everywhere he washes keeps getting dirty and muddy again as he washes higher up. He goes to Mika the Mechanic and together they come up with a way to use more water to wash Zerbies. They try it on Zack but he just gets thrown upside-down by the water. They decide another answer must be out there. When they are looking Walter washes some dirt off Zack's roof. That's when he notices it's easier to wash from the top down because the water goes down, taking the dirt with it.