An artistic, individualist Gummi who was stranded on a deserted island for twelve years with his best friend Artie Deco, a wise talking toucan. Tummi and Gruffi were shipwrecked on Gusto's island, just as a volcano was due to erupt and cause the island to sink into the sea. The three bears worked together and brought Gusto home with them to Gummi Glen during season 2. Gruffi tends to argue with Gusto for his outside-the-box thinking, and how much influence he is on Cubbi and Sunni. He lives by himself in a makeshift apartment behind a waterfall, but lives in Gummi Glen when the weather is too harsh.
Gusto and Tummi are the only Gummi Bears to wear sandals.