Rollercoaster, Lawn Gnome Beach Party of Terror!

While their mother is out shopping, the boy build a roller coaster. Dr. Doofenshmirtz and Perry battle due to the doctor's evil plan of throwing the earth off its rotation.
Phineas and Ferb's newest backyard project is to create a tropical beach paradise. Meanwhile, Perry tries to stop Dr. Doofenshmirtz's plan to steal all the garden lawn gnomes.