In Fabulous 3D (Episode One)

In Fabulous 3D is the first episode of (will insert name of series here). It is also the first episode in which we see September Mackintosh.

Summary
When a new girl moves in down the street, Phineas and Ferb are inspired to make an epic 3D projector. Elsewhere, Doofenshmirtz creates the Toyinator, a device which will turn anything it hits into a toy version of itself.

The Too Young Line
September: Excuse me, but aren't you a bit you-

Irving: Young? Oh yes. Yes, they are.

Ferb's Line
Ferb: Theoretically, if you invented a machine that had the ability to change the makeup of molecules, you could virtually create objects from thin air.