Executive Meddling: In 1940, Jerry Siegel wrote a story called "The K-Metal from Krypton" which would have introduced an early version of kryptonite and Superman revealing his secret identity to Lois. Siegel's publishers nixed this story as damaging to the franchise and made it clear Status Quo Is God would hold while both story innovations would have to wait for years.
Superman himself has dozens, to the point it's a trope in itself - the Superman Substitute. If they're not expies, they're parodies, and if they're not parodies, they're deconstructions, and if they're not deconstructions, they are lovingly crafted homages.
Lois Lane set the trend for news reporter love interests for superheroes who often fixate on the superhero identity before coming around to the secret identity.
Star-Making Role: Almost every actor who donned The Cape and blue outfit became a household name.
Tourist Bump: The city of Metropolis, Illinois, happens to share its name with the city the Man of Steel lives in, and takes full advantage of this. On June 9, 1972, the Illinois State Legislature passed Resolution 572, declaring Metropolis, IL, the "Hometown of Superman". There is a Superman museum, a 15-foot painted bronze statue of Superman in front of the county courthouse, and every year, on the second weekend of June, the city hosts the annual Superman Celebration, which is attended by fans from all over the world.
Tribute to Fido: The miniseries Superman for All Seasons, by Jeph Loeb and Tim Sale, gave teenaged Clark Kent a dog named Shelby, after Sale's own dog. It was a two panel gag, but Shelby later became more notable as the golden retriever in Smallville.
Jerry Siegel intended to have Lois learn Superman's dual identity early on and get a Relationship Upgrade back in 1939 or so; as it happened, this did occur... in the mid-1990s.
A man called Walter George Alton revealed in an interview that he was considered for the role of Superman but ultimately turned down for being too old. Mystery Science Theater 3000 fans may recognize him as the star of The Pumaman.
Sunsoft had made a game called Sunman for the original NES that, sadly, never got released. Its gameplay mechanics seem to hint, though, that they had planned to make this as a Superman game, but Sunsoft couldn't keep the rights to the Man of Steel and had planned to make a game using the engine they had made with original characters.
Factor 5 was working on Superman: Man of Steel, a Wide-Open SandboxSuperman game code named "Blue Steel", on PlayStation 3, Wii, and Xbox 360, as a tie-in to the cancelled Superman Returns sequel, then as its own Superman game, before being cancelled.
In 2000, a number of writers for Superman including Grant Morrison, Mark Millar, and Mark Waid, pitched an idea for a Superman reboot that would return the character to what the writers believedwas its roots. They believed that the Silver Age tropes that they saw as central to Superman was missing in Post-Crisis and they cited Clark's marriage to Lois as the problem. Their solution... Mr. Mxyzsptlk forces them to bargain their marriage in exchange for saving the world, and Clark and Lois would accept and this would lead to a reboot. If that reminds you of what happened to poor Spider-Man in One More Day, then it's probably not a coincidence that Mark Waid served as one of the consulting writers to Joe Quesada when he planned the reboot in 2005, and went on to write early issues in Brand New Day. In any case, Superman did get rebooted to a single status in the New 52 relaunch but this was a Continuity Reboot that didn't nullify and erase an existing relationship and love story as opposed to the Continuity Snarl caused by the Cosmic Retcon of OMD. And undoing Lois and Clark's marriage still proved so unpopular that it was eventually restored.
Due to DC's considerable financial woes in the 80's, the DC management seriously considered quite possibly one the biggest What Could Have Been's in the history of comics: Marvel's Superman! It would have been part of a bigger licensing idea that would have also included Batman, Wonder Woman, Green Lantern, Justice League, Teen Titans, and the Legion of Super-Heroes, with the possibility of full and proper integration into the Marvel Universe. The plan got far enough along that John Byrne, who would go on to create the foundational Post-Crisis Superman with The Man of Steel, made both a cover and a script to Superman - First Marvel Issue that have yet to see the light of day. The whole plan was eventually squashed when Marvel got hit with a completely unrelated anti-trust lawsuit and realized that it would be a bad look to basically absorb your only real competition while being sued.
. They believed that the Silver Age tropes that they saw as central to Superman was missing in Post-Crisis and they cited Clark's marriage to Lois as the problem. Their solution... Mr. Mxyzsptlk forces them to bargain their marriage in exchange for saving the world, and Clark and Lois would accept and this would lead to a reboot. If that reminds you of what happened to poor Spider-Man in One More Day, then it's probably not a coincidence that Mark Waid served as one of the consulting writers to Joe Quesada when he planned the reboot in 2005, and went on to write early issues in Brand New Day. In any case, Superman did get rebooted to a single status in the New 52 relaunch but this was a Continuity Reboot that didn't nullify and erase an existing relationship and love story as opposed to the Continuity Snarl caused by the Cosmic Retcon of OMD. And undoing Lois and Clark's marriage still proved so unpopular that it was eventually restored.