Bob tries to trick Auntie into invading Under, eventually carving a Floating Mountain into the shape of Russel's head that motivating Auntie to build a giant wall. This forces the Gorbal Birds to fly to Under instead of to their normal roost in Near Under. This upsets Russel since the birds start pooping on his newly constructed Roller Coaster (which he built since he's too short to ride one in Up).
