All-Star Superman is Grant Morrison's perfect distillation of what makes the Silver Age Superman Family so great. His Jimmy Olsen actually has a reason to wear different costumes and lead different lives. He writes a column called "For a Day", in which he spends 24 hours in some else's shoes. It's quite popular. Eagle-eyed fans will see all sorts of references to his Silver Age history in his apartment, like Aladdin's lamp, Firebird's costume, pictures of a Turtle Boy, hats that belong on Viking and pirates, and more. Just like in his 1960s series, you just never know who or what Jimmy will be next.
In "The Superman / Olsen War", Jimmy is P.R.O.J.E.C.T. Director for a day, a super-science thing on the Moon while the real director is off negotiating with light-based aliens. Jimmy puts on the guy's coat of many colors, a little spraynet in his hair, and he's off on the big classified tour, and soon making important decisions. One of these is what to do with Superman after he's dosed by black kryptonite, a new form of K from the Underverse, which makes Superman the opposite of what he really is. Bad, dumb, and as it turns out, progressively weaker. But he can do a lot of damage before he's out of juice, unless director Olsen can do something.
There's only one way to handle this if you're Jimmy Olsen, and that's to draw on the power of the Silver Age and TRANSFORM! And Which brings us to our BONUS JIMMY for the week - that's right - Doomsday Jim!
In the All-Star universe, Doomsday was a shelved super-soldier program developed by Cadmus, deemed to dangerous to exploit. DIRECTOR OLSEN SAYS DIFFERENT! They both run out of special effects before long and recuperate from their mutations. Sadly, Jimmy's column, which I'm sure he could have called "I Was PROJECT Director for a Doomsday", was redacted. Maybe they can run a repeat, like "I Was an Elastic Legionnaire For a Day", that was a good one. (Coming soon to a Snapshot near you!)