My son was taking a physics class at another university and said his professor had a fluorescent bulb unplugged but lit up on the front desk in the lecture hall. He couldn't get the professor to explain how this was done and so called and asked me. Oh, boy...., I wanted to know if he heard any hissing or crackling due to high voltage discharge. No, he didn't. Hmmm. :-(
It took me a while to get a similar demo going and I'm still trying to figure out how to make it portable, so I can carry a lit bulb up to the check out counter in a store and ask how to turn the bulb off. Also I like to tell the story about my younger son who was asked in middle school to weigh light. Naturally he comes home and asks me. I said with my unplugged shining bulb that he should weigh it. Then I squeezed the lamp so the light was gone and said that he should weigh it again and take the difference. What do you think? ;-)
See Plasma Flasher.