Best prank you've pulled off?

Way back when they used to use those tubular headphones on airplanes my brother did one of the funniest things to my Grandma on a flight to Hawaii. We were in the middle section of a 747, my mom, then bro, then grandma, then me... four across.

He took my mother's cigarette out of the tray and sucked a big drag, pulled my Grandma's headphones out of the socket feeding the sound from a movie she was watching, and puffed the smoke thru her headphones. She sat up startled as smoke poured out of her earphones, looked like her hair was on fire. He then started talking into the tubular hearing device that, "this was the Captain speaking", and they would be, "deplaning as an elderly woman's head was on fire". My poor Grandma's eyes just got huge.

I got very close to throwing up I was laughing so hard. Think I was 16 at the time and I will never forget it.