UP the 3D Pixar movie

The movie UP was a cartoon, therefore it wasn't real. But if they wanted us to think it was real, like the 3D suggests they do, then why did they have the house being flown by balloons? I mean, I might have believed it if they used some viable technology, but I'm not stupid enough to believe that the house was really flown by balloons. I did like Kevin the bird, though, who seemed very real. -AF