Batman's origin story was so perfect that it remains virtually unchanged more than 80 years later. Even movies have changed little about the Dark Knight's origin. The origin works so well because it so effectively communicates everything readers need to know about Bruce Wayne. Despite this, some comic creators have made small tweaks to the origin. A common trend is connecting the mafia to Martha and Thomas Wayne's deaths. Few retcons of Batman's origins have ever been as ridiculous as the one written by Batman's own creators though. Detective Comics #235 reveals that Thomas Wayne was Batman before Bruce, and the story only gets sillier from there.
It all begins with Bruce and Dick rummaging through Wayne Manor's attic when the Boy Wonder stumbles upon an old Batman costume. Bruce suddenly remembers that his father once wore the costume to a masquerade ball and reasons that the costume must have inadvertently inspired his own costume. Delving further, they discover an old film reel which shows Thomas at the masquerade ball when it's interrupted by a man with a gun demanding to see a doctor. Bruce cheers on as his dad punches the criminal out. Unfortunately, the hired thug threatens to kill partygoers unless Thomas follows him. The first Batman is then taken to treat a wounded crime boss named Lew Moxon. Away from innocents, Thomas cuts loose and whales on the criminals before calling the police. As Moxon is being hauled away, he tells Thomas that he'll have his revenge, and he'll hire someone else to do it.
All of these revelations prompt the world's greatest detective to realize that Joe Chill was hired by Moxon. With Robin and Thomas' costume in tow, Bruce goes to confront the man responsible for his parents' death. After battling some goons, the dynamic duo captures Moxon and takes him to the police. When Moxon passes a lie detector test, Robin encourages Batman to wear his father's old costume and then confront Moxon. The mob boss nearly has a heart attack at seeing Bruce, running away and protesting that the specter of vengeance should be dead. Though Batman gives chase, Moxon is run over by a truck. Bruce hangs Thomas' costume in the Batcave and declares the murder of Thomas and Martha Wayne finally solved.
Despite the Golden-Age goofiness of... all of that, the comic was considered canon until the DC Universe was rebooted with the world-shattering Crisis on Infinite Earths. Even after that, Moxon would briefly resurface in the '90s, though it is deliberately left unclear whether he had anything to do with the death of Thomas and Martha. The story would resurface again in 2008 when a villain stole Thomas' bat costume and claimed to be a resurrected Thomas. Bruce himself would even wear his father's bat costume while he was time traveling in the aftermath of Final Crisis. The big reference though would come with Flashpoint's murderous Batman, where Thomas Wayne once again became Batman, though under much darker circumstances than here.
Even with these later references, it's difficult to shake how ridiculous the whole thing is. The mob just randomly breaks into a costume party hoping there's a doctor there. Thomas is somehow an incredibly competent fighter, despite having no training. A doctor defeated a mob boss while wearing a bat costume, but no one thought to investigate the mob boss after the doctor was murdered? Batman is already a pretty silly concept in a lot of ways, with Batman's superpower just being Batman, but all of this is a little too much.
Still, there is such an earnestness to the story that it's hard to really dislike. If anything the ridiculous elements make what should be a boring retcon into something so wild that it's impossible to look away. Thomas Wayne's time as Batman in Detective Comics #235 might have been brief, but 64 years later, it's still an entertaining story that provided fertile ground for future writers and artists to explore.