From the AP obit, on his Riddler experience:
“It really was a catalyst for me,” Gorshin recalled in a 2002 Associated Press interview. “I was nobody. I had done some guest shots here and there. But after I did that, I became a headliner in Vegas, so I can’t put it down.”
In 2002, Gorshin portrayed George Burns on Broadway in the one-man show “Say Goodnight Gracie.” He used only a little makeup and no prosthetics.
“I don’t know how to explain it. It just comes,” he said. “I wish I could say, ‘This is step A, B and C.’ But I can’t do that. I do it, you know. The ironic thing is I’ve done impressions all my life — I never did George Burns.”