When Eric needs to get £35 to pay the window washer, he is forced to break Claire's piggy bank to get the money. In doing so, he finds her diary and discovers she wants a pony. Finding that a pony is out of his price range, he gets a smelly donkey with removable ears. When Claire insists the donkey go in the Gymkhana at school, Eric has no choice but to enter the old thing in the competition. Meanwhile, Brian and Maria raise havoc with a chemistry set.