Cheech and Chong (search) may have joked about marijuana in their movies, but the comedians say they didn't touch the stuff when the cameras were rolling.

"We tried one time and we wasted so much film," said Tommy Chong (search), recalling a scene in "Up in Smoke." "We were in the car waiting for the cue, you know. And the camera's rolling and we're sitting there, you know, and neither one of us heard the cue."

Chong and former partner Cheech Marin (search) appeared together for the first time in 20 years at the U.S. Comedy Arts Festival.

Chong said he isn't ashamed of introducing millions of Vietnam-era kids to marijuana (search). "When you think of how many kids died drinking alcohol, I feel I've saved millions of lives," he said.

Marin said their humor was appreciated by an unexpected group: "Cops were our biggest fans. Because they dealt in what we were dealing with everyday, but in reality... they saw the essential humor and they laughed."

Marin and Chong, who recently completed a nine-month sentence for trying to sell marijuana pipes on the Internet, said they are writing two new films, "Grumpy Old Stoners" and "Lord of the Smoke."