Like the other characters of the series, Perry was structured in a simple style to allow young viewers to easily draw him. In keeping with the show's general design scheme, Perry is constructed of geometric shapes in a style reminiscent of deceased Looney Tunes animator Tex Avery. Povenmire uses different design styles for drawing Perry depending on how he is portrayed. When Perry is portrayed as a domesticated and mindless pet, Povenmire begins with a square shaped like a loaf of bread. He then draws his front legs and feet before drawing the bill, which is set at a certain angle. Povenmire then draws his eyeballs, which are never focused and look in opposite directions in a daze. He concludes the figure by adding his hind legs, tail, hair, and finally color.
When portrayed as a secret agent, Povenmire starts with a similar bread loaf square design, but draws it standing up vertically and places a fedora on the top of his head, which is combined with the square torso. In contrast to his mindless and wild-eyed expression as a pet, the secret agent version of Perry is detailed with eyes "full of steely blue resolve." Povenmire proceeds by drawing his arms, which bear hands that are open and prepared for fighting or any danger. His legs are bent, as well prepared for an act of danger or action needed. Povenmire finishes the design by adding his beaver tail and color.
note some of this information is from Wikipedia.