Everyone wonders if Danville will be saved
"Perry, if you turn yourself in, I promise not to hurt your friends"
Phineas and Ferb's alternate selves join the resistance army to defeat Dr. Doofenshmirtz - 2.
"Buford, where are Phineas and Ferb?"
As Perry tries to save his family, a giant monster appears!
The rest is stuff we've seen before.