Loading into a hidden or pixel-sized iframe (or ilayer in NS) was a thing before XMLHttpRequest as well. In what would now seem a scary technique, you would use JS to load more JS (plus data, of course) that would put the new data into the iframe's host page.
I used Remote Scripting as well. It was a reliable enough hack that we built a lot of stuff on it. But I don’t think it was intended to be used that way when Netscape released JavaScript in ‘95.
