My favorite things about Phineas and Ferb:
1. The episode titles... seriously. "Are You My Mummy?" (that's a dialog line straight out of 'Doctor Who'!) "Run Away Runaway" (...80's song lyrics!), "Comet Kermilian" (a Boy George song), "Crack That Whip" (who doesn't love Devo?!), my two absolute favorites are: "Dude, We're Gettin' The Band Back Together" and "Lawn Gnome Beach Party of Terror".
2. The premise and dialog (AND JINGLE) surrounding Doofenschmirtz Evil, Incorporated. That Dr. Doofenschmirtz wants to take over (not the world but) the ENTIRE TRI-STATE AREA!! His arch-nemesis is secret agent, Perry the Platypus...! (Who is cool beyond words, btw.)
3. How these step brothers engage fully and with no holds barred in absolutely everything they do and get away with it! Fun Fun Fun!
4. There are too many allusions to count and I truly enjoy shows that do that.