"Doofus Khan's secret weapon", called as such by Princess Isabella, is a giant robot dragon created by Doofus Khan as a last resort method. He activated this after the princess escaped thanks to Phineas, Ferb, Buford and Baljeet.
The robot, while it was attacking the city, engaged in combat with a Giant Terracotan Warrior, and was about to win before Master Perry intervened, revealing It's weak spot so that the kids could take it out, the robot collapsing shortly afterwards.
The robot is based, and looks like, a giant dark green chinese dragons. It has a pair of long wings and four extremities, with fanged teeth.
The robot, thanks to It's wings, has the ability to fly and it can also shoot fire from his mouth. Doofus Khan can also manipulate it so that it can use knuckles and kicks.
- "Doof Dynasty" (First appearance)