"On Leather Wings" is the second-aired episode of Batman: The Animated Series, though the first to be produced. As such, it is also the first episode of the DCAU.
A mysterious creature is mistaken for Batman, and the police send a task force after the Dark Knight.
All seems quiet in Gotham City, until a half-bat/half-human creature ghosts past the Gotham Air One police blimp, breaks into Phoenix Pharmaceuticals, and assaults a security guard before stealing assorted chemicals from the laboratories. This is the latest in a series of such break-ins at pharmaceutical companies.
The report from the blimp and the wounded security guard leads Detective Harvey Bullock, after an unauthorized interview with Gotham Glazer, to petition Mayor Hamilton Hill for a special task force designed to eliminate the strange "Batman" that has appeared around the city. Commissioner James Gordon objects, stating that the police are already on the case, but the mayor grants the request and D.A. Harvey Dent promises Bullock immunity.
In the days following the Phoenix break-in, Batman investigates the robberies. Sneaking into the crime scene by dosing the guarding police officer with knock-out gas, Batman is spotted by two scientists. They notify the police, and Bullock radios for his squad to join him at the scene.
Batman investigates and discovers an audio tape of the creature as well as some hair samples. The police task force tries ineffectively to trap him at the crime scene but ends up merely blowing out the third floor of the building, allowing Batman to escape with the samples.
As Bruce Wayne, Batman takes the samples to the Bat Exhibit at the Gotham Zoo, where he meets a married couple on staff, Drs. Kirk Langstrom and Francine Langstrom, and her father Dr. March. Dr. March seems quite obsessed with bats, which he insists are the only creatures able to survive the next evolutionary cataclysm, while humans aren't. Bruce asks the zoologists to analyze the evidence from the crime scene, passing it off as a pest problem at Wayne Manor.
In the Batcave, the Bat-Computer has failed to match either the sounds or the hairs with any species known to man. Dr. March calls back and gives a perfectly plausible scientific explanation: the hairs are from a common brown bat, while the sounds are actually a mixture of sounds from the bats and a nest of starlings fighting in the chimney. The explanation proves false, given the Bat-Computer's inability to find a match with either species. Batman concludes that March is lying, and the zoo staff are somehow involved.
Later that night, Batman enters the zoo laboratory and finds Kirk working alone. Working from his father-in-law's theories, Kirk has created a formula that temporarily transforms him into a Man-Bat creature. Kirk has become addicted to the formula, to the point where he thinks of the Man-Bat as its own independent being, taking the necessary steps to continue its existence, such as stealing the chemicals necessary to keep making the formula. Now that he has destroyed Batman's evidence, Kirk is only one component away from a formula that will make the transformation permanent, but now Batman has interrupted the process.
Then Kirk finally transforms and attacks. When the first Man-Bat recoils at the sight of his wife who came to his lab, he leaves in shame. In the fight, the Man-Bat drags Batman through the sky across half of Gotham. Both of them fly past Gotham Air One, allowing Gordon and Bullock to see that the Man-Bat and Batman were in fact two different people.
Batman manages to subdue the Man-Bat. Taking him to the Batcave, he analyzes the chemical makeup of the formula and reverses the transformation. He then delivers an unconscious but fully-restored Kirk to his grateful wife.
This episode was the first one to feature Batman bleeding. Bruce Timm stated on the DVD commentary for this episode that he and Paul Dini fought with the censors to allow this shot, which was deemed inappropriate for younger viewers.
Producer Eric Radomski says in the commentary that he had a crush on Meredith MacRae, the voice of Francine Langstrom.
Batman answers Dr. March's phone call saying "What's up, Doc?", Bugs Bunny's catchphrase.
Dr. March's line "They're survivors" of referring to bats was similarly said by Batman in Tim Burton's Batman that "They're great survivors".
This marks one of the very few times in the series where Batman speaks using Bruce Wayne's voice, which later happens again in "Heart of Steel, Part I".
For the Batman Beyond episode "Splicers", Will Friedle was given a tape of this episode to help him prepare for voicing Terry McGinnis's Man-Bat transformation.
This episode's opening where Man-Bat's flying through Gotham is reversed shot for shot in the end of the Justice League Unlimited episode "Epilogue" with Terry McGinnis. Also, the blimp pilot (voiced by Kevin Conroy) who asks "Did you see that?" is mirrored by a Gotham police officer (also voiced by Conroy) asking the same question as the last line spoken.
In the Justice League Unlimited episode "Destroyer", Batman (voiced by Conroy) says the second to last line to Superman which mirrors Conroy voicing the second line of this episode.
The opening of the episode is also mirrored in the opening scene of the Supernatural episode "Like A Virgin" with a small plane passenger asking the pilot if they "saw that" flying outside the window that looked like a large bat. Perhaps in respect to this, Batman is mentioned later in the episode.
Although this was the first episode made, the first aired episode of the series was "The Cat and the Claw, Part I", likely due to the success of Batman Returns.
Danny Elfman's theme from the first Batman movie is strongly used in one scene.
In the robbery report on the Batcomputer, the Carson Chemicals burglary is misspelled "buaglary".
Kirk Langstrom's formula would later be the basis for Abel Cuvier's Splicing formula in Batman Beyond, and Professor Milo uses Kirk Langstrom's notes for use by Project Cadmus's genetics division in Justice League Unlimited.
Dr. March continues Langstrom's research and subsequently, Francine Langstrom becomes the Man-Bat albeit accidentally in "Terror in the Sky".
In the later episode "Tyger, Tyger", Langstrom identifies the base chemical for his fomula as the invention of Dr. Emile Dorian.
Batman was subsequently framed again by a crime that he didn't comit in the feature movie Batman: Mask of the Phantasm.