Clayface is a large meta-human made of a reddish brown clay. In his regular form he has a rippled and waxy appearance, with all defining facial features made up of the clay, however he can also exactly replicate the appearance of anyone.
Karlo was corrupted by the incident that transformed him into Clayface and utilized his superb acting skills in a life of crime. Because of the nature of his clay body, Clayface is easily motivated by his need to protect his body's integrity and ability to transform.
Basil Karlo was a famous actor who was transformed into a super-malleable clay. He turned to a life of crime and took the name "Clayface." With his superb acting skills, coupled with his ability to look exactly like anyone or anything, he seamlessly impersonated people in his schemes.
Scooby-Doo! & Batman: The Brave and the Bold
After getting a clue from Riddler, Batman and Mystery Inc. found a strange clay footprint in a crypt at Arkham Cemetery. The clue was taken to the Batcave, where the gang analyzed it as Batman returned to Gotham Chemical Storage to confront Crimson Cloak. The clay eventually attacked the gang and they neutralized it with the Batcave's dehydrator. Modifying the dyhydrator to be portable, the gang went to Batman's aid as the Bat Gang and neutralized the Crimson Cloak, who was revealed to the Mystery Analysts of Gotham as Clayface. He explained that he had become infected with a bacteria strain that was breaking down his clay structure and Riddler promised him a cure in exchange for his help framing Mystery Inc. and rebuilding the Teleportation device. Upon the realization that Riddler had masterminded the crime, Batman was able to deduce that Riddler was not locked up in Arkham Asylum as they believed. A guard discovered that the Riddler in the cell - who Batman and Mystery Inc. had previously spoken with - was just another Clayface impersonation.