Killer Croc (Waylon Jones) is a fictional character in the DC universe, an enemy of Batman. Created by writer Gerry Conway and artist Gene Colan, he first appeared in Detective Comics #523 (February 1983).
Once he was a cocaine/arms dealer until foiled by Batman and Robin.
Killer Croc has been depicted as being so animalistic that the Swamp Thing was able to summon him to the Louisiana bayous.
Over time the primal reptilian part of his brain gains more control of his psyche. He possesses superhuman reflexes and speed. Croc also possesses the superior senses and underwater capabilities of his namesake.
Later in the series, Croc would serve as nothing more than comic relief. In the episode "Almost Got 'Im", a group of villains are discussing how they almost defeated Batman. While everyone else had managed to almost kill Batman with a complex deathtrap or such, Croc proudly proclaimed that he once threw a rock at Batman. However, this was later revealed to be Batman impersonating him. Still, in the episode "Trial", when Batman is put on trial by all the prisoners he's put in Arkham, Croc is among the quasi-jury shouting "Hit 'im with a rock!!"
Baby Doll seems to have a crush on him, until she overhears Croc boasting about manipulating her to a pair of clingy women (implicitly prostitutes), she betrays him to Batman and Batgirl, and in the ensuing fight, he is defeated after being drenched in boiling water. He makes his final appearance in the later episode Judgment Day, where he is seen trying to get Penguin to pay him for jewels he had stolen for him. The Judge (Two-Face in disguise) attacks and defeats him soon afterwards. He is voiced here by Brooks Gardner.
In 2005, an episode of the animated television series The Batman featured Killer Croc, voiced by Ron Perlman. In this version Croc is even more reptilian than past versions and has a tail. He appears to be much stronger than Batman and much like a crocodile, he's able to stay underwater for long periods of time. His origins are mostly unknown: one of his henchmen tells Batman that there are different rumors: that he is a military genetic experiment gone awry, that he deals with the wrong kind of voodoo magic in the swamps, he is simply a genetic freak, or that his mother didn`t want him and flushed him down the toilet and all the acid in the sewers mutated him.(it is never explained which, if any, story is true). He recruits three criminals (two of them voiced by Jim Cummings) as henchmen to help him flood Gotham City. This animated version also speaks with a Cajun accent and has two pet crocodiles to do his bidding. Batman later deprived him of his air supply enough to be taken down and left for the police to arrest him and his henchman (remarking that "Crocs may like water but they're no fish"). He later returns as part of Penguin's Team Penguin. Killer Croc and his henchmen later appear as one of the captive victims of Rumor after he ambushed Killer Croc and his henchmen in their hideout. Croc makes his final appearance in "The End of the Batman" where he, Penguin, Ventriloquist and The Joker team up to commit a crime spree now that they are under the protection of the vigilante Wrath.
In this version, Waylon Jones is a cannibalistic serial killer. The urban legend in the segment goes that he was an infant born with a rare skin disorder who had been abandoned by his mother, leaving him in the sewers of Gotham City. His skin disorder made his skin reptilian, and his teeth transformed into serrated replacements. He thus becomes a circus sideshow performer for a time. Later, Jones - now called Killer Croc - goes on a killing spree that eventually lands him in Arkham Asylum. There, his homicidal impulses intensify during treatment by college professor Jonathan Crane, who infects him with his fear toxin. Croc escapes from Arkham and flees to the sewers along with Crane (now known as The Scarecrow) and a handful of escaped Arkham inmates.
When Scarecrow orchestrates the kidnapping of Cardinal O'Fallon, Croc infiltrates the church and carries him down into the sewers. Batman comes to investigate, and Croc attacks him, biting him and infecting him with the fear toxin that is coursing through Croc's own body. After a lengthy battle, Batman fends off Croc by shoving a smoke grenade into his mouth.
A screenshot of Killer Croc from Batman: Arkham Asylum appeared in the September 2008 issue of Game Informer, issue 185, on page 71. He is chained up and is extremely large, towering over Batman and the guards that surround him. Killer Croc will also appear in Lego Batman: The Video Game.