Arthur and the Great Adventure

Arthur did as a boy what only grandpa, a fellow nature buff, did as an adult: pass, as white man, the Bogo tribe's tests of harmony with the natural worlds of trees, minerals and animals. To answer a mysterious call fro help from the Mimimoy people, he enters their world miniaturized. By the time he works out with friends it was a trick, the mastermind has already escaped, ready to strike in our world.