For one thing, outside of its spec fic premise, Phineas and Ferb is a really good show in general. I could write whole other articles on how it’s a blisteringly funny satire of contemporary pop culture, or how it’s a loving portrayal of a blended family that treats divorce and remarriage as normal parts of life, or how it’s remarkably cleverly written using repetition, variation, and song to create complex and compelling characters, or how the secret protagonist of the show is actually Candace, the teenager trapped between her desperate need to be an adult and her own childish desires to have fun.
All that aside, Phineas and Ferb is a great science fiction, by which I mean it uses an impossible world to tell real stories about real people.
If you've been putting off watching P&F, let Steve Padnick convince you otherwise. It really is one of the smartest, cleverest, funniest, coolest TV shows currently airing and proof that not all American animation is brain-dead or made by Seth McFarland.
Also, name me a TV show that manages to have a song per episode that doesn't suck and is still original. Glee is automatically the wrong answer, by the way.