On phineas and ferb the show. Are isabella and staci sisters?
No they aren't sisters at all. They just both have similar appearances (black hair, hair bows, etc.) They are about the only people on the entire show that are not related to another character, actually.
I agree, it is just simply a coincidence.
I don't believe so, but they definitely look alike!
No, I thought they were but, they're not. There is no real explanation for this, though.
No. I like your profile pic
No but they do look alike
No they are not proven in the episode Robot Rodeo which this episode was made to prove that theory wrong!