After an early inspection, Phineas And Ferb build an eye that can see through everything. Meanwhile, Doof had a ColossiInator that can turn things into buildings, but then Phineas and Ferb's eye got turned into a building. The boys tried again to build the eye....
The day after, Doof had taken revenge on Perry. Then Perry gets to turn Doof into a building.
Buford: Wow! That's a big eye!
Baljeet: Yes, yes it is.
Phineas: Wow, I did not see that coming.
Ferb: Yep, I didn't too....
Phineas: OK. Almost done.
Issabella: Hello, Whatcha Doin'?
Phineas: We're building an eye to see everything
(He Went Into A Sock)