Rabbit is digging a ditch with Piglet and Pooh to save work. he plans to fill it with water to fill it with water to water his garden, but Gopher fills it in... He tells Rabbit he almost ruined the work of a life time and shows them a special blackboard - an equation for The Ultimate Tunnel... His Grandpappy once accidentally tunnelled into the Grand Canyon and ever since then he's had the dream... Gopher's tunnel is to start at... Rabbit's house... Pooh accidentally smears hunny on Gopher's blackboard... Much to Rabbit's delight... And he puts some bogus equations on the board. However the equation involves Piglet's house... Tigger's house... Pooh's hunny tree... Pooh confesses to Tigger, and Piglet... They try to change the equation back... Rabbit is trying too, but he doesn't know how, but they try their hand at Tiggernometry anyway, and they try to dig Grandpappy's Ultimate Tunnel...