User blog comment:Disneygirl94/Phineas and Ferb: The Beak. Anyone else love it?/@comment-1758246-20100310035302

Doof would have to fit into the abdomen, which would be extremely cramped for him, to control everything. Unless the upper body had full control of the body too...

Knowing Phineas and Ferb built it, they probably made it so that they could exchange control from time to time.