Tommy has decided that he wants to grow up to be just like the famous Sir Nigel Thornberry, whose animal safaris he loves to watch on TV. He and the Rugrats gang are just about head off on a their own new adventure with their families on what is suppose to be a splendid, luxurious cruise. Unfortunately they wind up stuck in a dumpy little "pleasure" boat which gets them shipwrecked on a deserted island. Tommy decides this is exactly the sort of place Sir Nigel Thornberry would be, and he and the babies head off into the jungle to look for him...