Animate an Objecg on a slide

What do you mean by animate? You can do "builds", which makes objects and text appear and disappear on the slide with various effects. But Keynote does not have any other animation tools natively available (for example, you can't move an object along a path).

There's some evidence that the next update to Keynote might include some of this functionality, but nothing is certain on that score.

If you provide some more detail about what you want to do, it may be that folks here can offer some more specific advice.

Yes, you'd need to do this either as a Quicktime movie or in Flash. I'm sure others here could advise you on the best approach, as that's outside my bailiwick.