Chuckie (Nancy Cartwright) and Tommy (Elizabeth Daily) find themselves stranded with their parents on a remote island. By coincidence, the adventurous Thornberrys are also exploring the island. So, with his talking dog, Spike (Bruce Willis), in tow, Tommy takes Chuckie on a walkabout meant to find Donnie Thornberry (Flea) and his sister, Eliza (Lacey Chabert). They'll need to be careful, though, as exotic leopard Siri (Chrissie Hynde) is hungry and not afraid to make her presence known.