My philosophy teacher in high school used to smoke a pipe, walk around smoking it while lecturing. (They probably can't do that anymore, secondhand smoke, blah blah.) Anyway, one of the stoner girls in class threw some weed into his bag of tobacco while he was out of the classroom for a couple minutes. The teacher fired up his pipe as normal, and we could all smell the pot. But he didn't notice, and gave a fucking great lecture that day!