Here's what I've cobbled together. In the Doomsday Jimmy issue, when Superman was exposed to black kryptonite from the Underverse, he started talking like a Bizarro and stuff. From what I see, the Underverse is the opposite of our universe, where people talk backwards and such. Or something.
Anyways, Superman stated himself that the Bizarro we saw in this issue happened when one of PROJECT's Bizarro workers touched him and instead of him becoming infected like the fat black girl did, it spawned that Bizarro.
As for my opinion, I loved it. Morrison has managed to take the Silver Age, which I've always loved, and he's brought a post-modern feel to it. It's the Silver Age for the 21st century and I love it. I'm a hardcore Superman fan, as many of you know, and All Star Superman is at the top of the list of the Greatest Superman Stories Ever Told, along with Superman For All Seasons, Whatever Happened to the Man of Tomorrow, Must There Be A Superman, etc. I dare say it's the greatest Superman story to be crafted since the days of Siegel & Shuster.
For this issue in particular, I absolutely LOVE the idea of Zibarro. One in every five million Bizarros is basically retarded, like one in every so number human children is mentally disabled. But with Bizarro laws, retarded in their society means that the Bizarro is handsome, intelligent, and morally right. So Zibarro, the idea of Bizarro's Bizarro, is just amazing. I love it and I love his costume. Love it. Have I said love enough in this post yet?