In this episode, we meet Rosy and Wally. They both want to play on the seesaw and try to play on their own -- but it doesn't work. Rosy tries to use a balloon at the other end and it is too light. Wally tries to use a large stone but it is too heavy. They then realise it is more interesting and successful if they play together! In this episode, preschoolers about light(weight) and heavy.