Carl the Collector Episode 8 A Forrest of Plans/The Marble Collection >In a hot summer day, Carl and Arugula build a marble run together. Frustrated at their frequent failed attempts at building one, they decide to instead join Forrest at his water slide. After Forrest reveals that he had successfully built the water slide by learning from his own failed attempts, Carl and Arugula return to continue building their marble run, eventually succeeding in building a functional one that they show Forrest.