Jossed: A scientist baring a striking resemblance to Strange appears in a flashback to Bane's origin story on how he received Venom. While helping to create a Genius Bruiser, giving him a Fantastic Drug to make him bulkier, and unleashing him against Batman is exactly the kind of thing Strange would do, it wasn't him, and seems to be a coincidence.
Name's the Same: The name "Red Robin" sure would sound more intimidating if it weren't the name of a fast food franchise. Especially if their slogan weren't:
Red Robin! Yuuuuuum!
Cassandra Cain to Kate Kane, at least in terms of sound.
And Katherine "Kate" Kane to Cassandra Cain, sound-wise.
A very confusing example with Doctor Simon Hurt. Lincon March also claims to be Thomas Wayne Jr., and may in fact be Bruce's long-lost brother.
Recycled Script: One of Hugo Strange's earliest stories had him unleashing a fear-inducing powder on Gotham City; the Scarecrow debuted less than a year later (though he didn't use his fear gas then).
Science Marches On: The character's been around for over 70 years, so this is a given. For example, Batman started out in the 30's as a rich guy in actual tights with a Bulletproof Vest, a silk rope, smoke bombs, and a souped up but otherwise normal car. Nowadays he wears a full suit of kevlar armor loaded with high tech gear, military level weaponry, and the Batmobile along with nearly every kind of vehicle he could need. Although as things like carbon nanotubes become more common in the future, it'll be interesting to see how the writers can maintain the dramatic tension when the batsuit seems damn near indestructible. The writers of Batman Beyond successfully maintained dramatic tension when Terry was going around in flying power armor. When technology reaches the point where the Bat-suit has carbon buckytube armor, that only means the Joker will be shooting at it with a rail gun.
On the flipside, Batman's aerial vehicles are rarely seen these days over Gotham, as the risen level of civilian air traffic and -surveillance would make that a safety and secrecy hazard much more than in the old days.
What Could Have Been: This image◊ was created in case Jason Todd was voted to survive A Death in the Family. A very similar colored version (here◊) was printed in Batman Annual 25, which recounts Jason Todd's resurrection, as well as the reality-warping that caused it.
Dick was going to be Killed Off for Real in Infinite Crisis. For the same reason that saved him in fact. Considering how much emotional weight came from Barry Allen's death he could have been gone a while...
In the early 00's, there was brief talk at Warner Brothers of possibly making a live action Batman Beyond movie to reboot the Batman franchise but the idea was passed over for Batman Begins instead.
Hawkfire almost got featured, alongside Beast Boy and a host of other 1970s characters, in a spin-off called Titans L.A. As Bat-Girl, she was initially set to be part of the main '70s Teen Titans team and be involved in a love triangle with Robin and Duela Dent, but DC pulled the plug on the title before Bob Rozakis could get to those plans.
Awesome, Dear Boy: The reason several of the guest-stars took the gig as villains. Victor Buono as King Tut is the best example: he was a huge (no pun intended) fan of the comics, and was so into the series he made more appearances than any other guest-star outside of Newmar, Romero, Meredith, and Gorshin.
Beam Me Up, Scotty!: Sort of. Robin's infamous "Holy [relevant phrase]!" Catch Phrasewas used constantly, but he usually didn't end it with "Batman!". He did occasionally, but not nearly as much as the phrase's popularity would make one think he did.
Briefer Than They Think: The series only ran for a year and a half from 1966-68, but since most of the series' stories were two parters, that means 120 episodes were produced for a suitable syndication package.
Dawson Casting: Burt Ward was twenty, married, and had a kid on the way when he took the role of fifteen-ish Robin.
The Other Darrin: Julie Newmar was replaced by Lee Meriwether as Catwoman for The Movie, and then by Eartha Kitt for the final season.
Also with the Riddler, who was replaced by John Astin for his penultimate appearance after a dispute between the producers and Frank Gorshin.
Mr. Freeze had it the worst however, as he had a different actor every time he appeared; George Sanders played him in his first appearance, Otto Preminger played him the second time, and Eli Wallach was the third and final actor in the role.
Real-Life Relative: Shame's fiancee, in "The Great Escape"/"The Great Train Robbery" was played by Cliff Robertson's then-wife, actress Dina Merill.
Recursive Adaptation: 2013's Batman '66 comic book series is an adaptation of this series, which of course was itself an adaptation of the Batman comics that had been printed up to that time.
Short-Lived Big Impact: This show pretty much defined the Caped Crusader in the public eye for decades (and seemingly permanently in Japan), but the TV show itself only ran for two years.
Throw It In: Burgess Meredith made up The Penguin's squawking laughter to mask the cough smoking gave him.
Spencer Tracy was offered the role of The Penguin, but would accept only on the condition that the series got to end with him killing Batman.
The "Batbook" a book filled with trivia on the series, revealed that Dozier also had the late Mickey Rooney in mind for the part, but he couldn't work it into his schedule.
Also, Two-Face was once considered as a villain for the show, only his origin would be that he was a TV news anchor who had a TV set blow up in his face. Clint Eastwood was even considered for the role but the character was ultimately dropped because he was considered "too gruesome" for such a light-hearted show. Imagine Clint Eastwood playing Harvey "Two Face" Dent. Yeah. Damn Executive Meddling!
Jose Ferrer & Gig Young were both considered for the Joker.
The season 2 episode "The Puzzles Keep Coming/The Duo is Slumming" was originally written for the Riddler note with the titles "A Penny For Your Riddles/They're Worth a Lot More" , but with Frank Gorshin having contract disputes with the producers, the similar Puzzler was created instead.
Robert Morely was originally supposed to play the Sandman, but quit after the episode was rewritten to include Catwoman note the producers had guaranteed another Catwoman episode, so they had Charles Hoffman rewrite the Sandman episode to include her, since it was cheaper than making another one . This led to Michael Rennie getting the part, whom the co-writer felt was "too stiff," resulting in him disowning the episode.
Bette Davis was apparently in the running to play Ma Parker.
Tim Burton once said of the film "I liked parts of it, but the whole movie is mainly boring to me. It's OK, but it was more of a cultural phenomenon than a great movie." He also wasn't horribly enthusiastic about how Prince's songs were used in the film.
Main screenwriter Sam Hamm, one of the many writers who worked on the script, has also absolved himself from the sequence where Alfred leads Vicki to the Batcave, a move that didn't sit well with a lot of fans. Hamm said the scene didn't come from him and that the day Alfred let someone in the Batcave would be his last day of employment. It gets a Call Back in Returns.
The Danza: Jack Nicholson as (pre-Jokerization) Jack Napier.
Enforced Method Acting: Keaton hated the Batsuit because he suffered from claustrophobia. Elfman and Keaton both decided that it would enhance his performance. And it did.
Executive Meddling: This was a big reason the Schumacher films turned out the way they did, but again, Burton's films weren't immune.
The Axis Chemicals set was originally the xenomorph hive from Aliens. The crew had to remove most of the xenomorph webbing before filming, but bits of it can still be spotted if you look carefully enough.
In the original script, written by Tom Mankiewicz, crime boss Rupert Thorne hires Joe Chill to murder Thomas Wayne because he is running against Thorne for city council.
A later draft written by Sam Hamm also has a large part of the film concentrating on Bruce traveling abroad and training with Henri Ducard, whom Bruce would later discover to be a film. This script was later overhauled into the version seen in the film, and Ducard was deleted. Months before the film's release, then-DC Comics editor Denny O'Neil asked Hamm to guest-write a "Blind Justice" storyarc throughout Batman-themed comics as a tie-in, and Hamm introduced his character there (specifically, in Detective Comics #599, April 1989). Ducard would later appear, played by Liam Neeson, as a Composite Character with Ra's al Ghul in Batman Begins.
Burton stated in an interview that he had initially wanted Adam West and Julie Newmar, from the 1960s series, to play Thomas and Martha Wayne in the flashback. Audiences would recognize West and Newmar from the series and see them get shot, symbolizing the "death" of the old Batman. Script rewrites caused this to be scrapped, and West later said he wasn't even offered the role (and even if he was, he wouldn't have taken it).
Sean Young was originally going to play Vicki Vale before Kim Basinger. Young had to bow out at practically the last minute after breaking her collarbone in a horseback riding accident.
That hooker who smiles at Little Jimmy in the film's opening scene? Originally, she was supposed to be only 14 years old. She was also going to be shown chatting casually with a couple of cops, showing us how corrupt the Gotham police are even before we meet Eckhart.
Some of the earlier drafts focused on Batman's origins and featured Robin.
This film went through so many different directors, screenplays, tones (including but not limited to straight up Adam West style parodies) and possible casts before we got the film we know and love today that there are truly too many to list here. Legend has it that Richard Donner himself, the man who directed the 1978 Superman film, was among the directors approached at one point to make this film, but had to decline due to previous commitments. Actors considered for Batman included Mel Gibson, Pierce Brosnan, Charlie Sheen, Tom Selleck and even Bill Murray opposite Eddie Murphy as Robin.