The portal crackled shut with a sound like a zipper closing on the universe. On one side: Danville, home, the familiar jingle of the ice cream truck. On the other side: a smoldering crater where the giant, robotic, and utterly evil version of Heinz Doofenshmirtz had just been erased from existence.
The story kicks off during the "Platypus Day" celebration, where Phineas and Ferb accidentally crash into Dr. Doofenshmirtz's lab. They help him complete his "Other-Dimension-inator," which transports the trio to an alternate Danville. Unlike their colorful home, this 2nd Dimension is a dystopian police state ruled by an alternate version of Doofenshmirtz who is genuinely competent and evil. Key plot points include: Phineas and Ferb- Across the 2nd Dimension -Nor...
, which serve as the backbone of Doofenshmirtz-2's tyrannical rule. Villains Wiki Design & Role Norm’s Second Dimension Directive The portal crackled shut
The hat’s influence spread like oil through his circuits. The real Doofenshmirtz had programmed him to love. The 2nd Dimension Doofenshmirtz had programmed his Norm to obey without question. And now, the two directives began to fight. The story kicks off during the "Platypus Day"
Compare the scripts/dialogue between the two versions of Doofenshmirtz regarding their robots