How come 601 comes after 602 and 603 ?

pourquoi?why?

and one more question:

what did Kenny say about Madonna before he died?

that dialogue translated by the Jew boy

It's been answered very recently in an extended thread. But, the short answer is that the #s are assigned first, but the episodes are not completed in order. Sometimes it's because the episode was hard to make. Also, sometimes, the network will decided to show them out of order for their own reasons.

You got the drift of it pretty well.