Some of them link to http://dynamicdrive.com/ , which is probably where Chruser / Wetwired got the script (looks like Chruser's handiwork, though)

I think it has something to do with the whole April 1st thing.. but maybe not. It IS messing around with my browser though, when they go offscreen it puts a horizontal scrollbar at the bottom (for obvious reasons), when they come back the scrollbar goes away (as you would expect). So I get a flashing scrollbar.