Actually, you'd be surprised at how common it is for people to be . . . um . . . infatuated with anime characters and such. I'm not speaking from personal experience, but rather for knowing several of these people and hearing about their friends and such . . .
There's a reason, though, that it happens a lot more than people "developing a crush on Kim Possible" as you said, Ed. Basically, anime is based on a very different aesthetic than American cartoons are; it's much more about visual beauty and captivating the audience with the art, whether you're talking about something brilliant like "Akira" or "Spirited Away", or something aimed at kids like "Digimon" or "Dragonball Z". American cartoons tend to be more about looking stereotypically "cartoony", and, as such, are much more free to be unabashedly silly and pointless, or to be very unsubtle parodies (as the Flintstones, and later the Jetsons, were of '50s family sitcoms).
Where anime focuses mainly on the visual and plot aspects of animation, American cartoons focus much more on endless humor/ridiculousness and parody.