Detective Ethan Bennett is a fictional character created specifically for the animated television series The Batman. He is voiced by Steve Harris, and made his debut in the episode "The Bat in the Belfry."
In the episode "The Rubberface of Comedy," Ethan's superior, Chief Angel Rojas, orders the entire police force to take down every masked and costumed "freak" in Gotham City. Ethan protests, defending Batman as an asset to the city and crediting him with helping to capture the Joker. In response, an infuriated Rojas suspends him.
When "Joker Putty" touches a surface, it turns it to just that: a malleable putty. When Ethan inhales it, the concoction infests his system, and transforming him into Clayface, a deadly shapeshifting monster who uses his powers to get revenge on Joker.
Clayface kidnaps Rojas and attempts to kill him, but is foiled by Batman and Yin, and escapes capture by slithering down a drain pipe. During a talk between Bruce Wayne and Yin in a diner, Clayface appears for a few seconds, and the two run after him. However, he disappears before they can catch him.
Clayface returns in the episode "Meltdown", where he goes to Arkham Asylum to kill the Joker, but Batman stops him. Clayface later goes on trial for his crimes, with Hugo Strange giving him a clean bill of mental health. He is put on probation: if he uses his powers again, he will be put back in Arkham. Clayface becomes Ethan Bennett again, and gets a job from his friend, Bruce Wayne.
When the Joker breaks out of Arkham to wreak chaos, Ethan becomes determined to save others from his fate, and becomes Clayface again in an attempt to stop the Clown Prince of Crime. At first, he and Batman work together to bring the crazed supervillain down, but after Batman confronts him for his violation of court orders, Ethan feels betrayed. He becomes Clayface permanently (or so as the people of Gotham thought), and is put back in Arkham.
In the episode "Grundy's Night," Clayface shape-shifts into the undead creature, Solomon Grundy, to loot Gotham City on Halloween, to take advantage of a supposed curse involving Grundy. He is encased in wax after a fight with Batman and put back in Arkham Asylum.
It is hinted in "Artifacts" that Ethan is permanently cured, and becomes the new Chief of Gotham PD in the year 2027.
As Clayface:
In the comic book, Clayface pulls a stunt similar to turning into Solomon Grundy and turned into Catwoman to frame her for his robberies. In "Hit and Run", he turns into Joker and steals the Batmobile to get Batman to find Joker's hideout so he can take his revenge. In "Escape," he is manipulated by Hugo Strange to steal a chip that would help him get rid of the "voices" in his head. However, Strange uses it to control him, and turns him into a giant designed to wreak havoc on the city. He is eventually freed by Batman, and the two work together to stop Strange.