You don't see Clark giving Superman the business on covers anymore, and I think we as a culture are poorer for it.

I have a small print of Superman #201 on my wall, a Curt Swan cover with Clark seemingly storming off, saying "I quit! I'm through being Superman--for good!" I don't think the story this issue is related, but the cover seems similar, and within a year of #201! Even still has a newspaper in his jacket pocket! I wonder if maybe the same editorial description or prompts were given to two artists. From 1968, Superman #209, "The Clark Kent Monster!" Written by Cary Bates, pencils by Curt Swan, inks by Jack Abel. Cover by Ross Andru and Mike Esposito.

An alien space capsule is causing tidal waves in Metropolis Harbor, and Clark Kent has to pretend to be headed for the hills, so he can duck out and change into Superman. Supes smashes open the capsule, revealing a creepy, alien brain. Still, the alien's brain-rays hurt Superman, but bounce off and destroy the alien, so problem solved? Except, when Superman lands in an alley to change, he finds his Clark Kent clothes and glasses gone, no longer in his cape-pouch! Stolen? No, Clark was already wearing them, as he confronts his alter-ego, glowing red and pissed off.

Clark then storms into the Daily Planet, and drags Lois with him, to go bring in the Marauder Mob. Clark tells Lois he's tracking the mob by their "brain-impulse residues" left at a crime scene, which seems unlike Clark somehow...He's also seemingly invulnerable, and able to use "mental domination" to turn the Marauders into meek cowards. Superman wonders, if he's just jealous of Clark, or is there something else to it...yes, you goof! The next page, Clark's made himself a Superman-like uniform, and smashes up the Planet office as he quits, even zapping Perry White with a weird vision-blast. Jimmy uses his signal watch to call Superman, who faces off with "Clark," who is of course the alien brain entity, which stole Clark's clothes, glasses, and brain cells from Superman!

Growing more big-headed, faux-Clark goes on a brief rampage, but can't bring himself to kill Lois: while it tries to assert dominance over the Clark-persona, Superman puts his plan into action. The brain still needed Superman's mind, so couldn't kill him yet, but Superman hypnotizes himself to forget his Clark Kent identity, cutting it off from the brain, which dissipates in space. Feels like Supes kinda killed that thing, or at least didn't go all-out trying to save it anyway. Later, with his memory and stuff back, Clark tells Lois that Superman told him about the creature "impersonating" him, then pretends to be scared of a yippy dog.

Also this issue: "The Super-Servant of Crime!" (Written by Robert Bernstein, pencils by Curt Swan, inks by John Giunta.) Superman had been mining gold for a charity drive, like 50 miles below a mobster's property; so to reimburse him agrees to carry out six requests, as long as he doesn't ask for anything illegal or repeat a request. Superman then repeatedly dicks the guy over, like a terrible genie, like "get me a lawyer, dawg." It's supposed to be cute and funny and just rubs me the wrong way.