I have always loved the level of technology freely available to people in the Batman the Animated Series universe. I would love to know if the Joker stole Captain Clown and then re-purposed him or build him from scratch or what? Bruce Timm should go back and just do an episode on the history of Captain Clown.
Considering that Joker lived in an abandoned version of the 1939 World's Fair's House of Tomorrow, complete with animatronic wife, I just assume Captain Clown was a forgotten General Motors prototype.
Also, the Bat-Computer was made out of Bakelite, according to Bruce Timm.
He wasn't living at the world's fair yet by this point in the series. I think that may have only been in one of the movies. When they introduced Harley the joker was living in an old fun house.
As for the bat computer, i don't think i ever saw that interview with Bruce Timm. Link?