If you're so worried about your butt getting big, Do Something about it, Ducky!!
Remember all that trouble you had getting airborne last year when rescuing that other duck? That might be a good start - Get thee to a second floor launchpad, and start working those flight muscles back into shape.
Go fly along following Sheldon on a bicycle, or even Gramp in the car. That'll burn off the excess flab post-haste, and get you back to Buns Of Steel.