This time Phineas and Ferb decide not to fritter away their energy. They are going to build the coolest rollercoaster in their backyard! But to assemble such an enormous construction they need a good drawing and a lot of different parts which are not so easy to find. And tattletale Candace is up to stick her nose where she doesn’t belong… And where is Perry the Platypus? He is on a secret mission again! Brave Agent P is on his way to save the town from another wicked design of Dr. Doofenshmirtz. Someone must help him! And, of course, one shouldn’t forget about building the rollercoaster.