It doesn't matter how much emphasis you put on the static problem when briefing a new ground crew, they always forget. Always keen to be the first to catch the hook, the new groundcrewman will reach out, grab the hook then snatch his hand back as the shock hits him- lesson learnt - they don't do it again.
I was caught out myself during a session with 4 pilots doing underslung training. The ground crewman was complaining that despite having a static discharge pole he was still getting shocked. I volunteered to go on the ground and "show him him how to do it". Holding the static pole in my hand, the aircraft (AS332L) came to the hover above my head. I touched the hook with the pole to discharge the static, put the pole down and holding the strop (which was touching the ground) I reached up to grap the hook. Although the aircraft had been earthed less than 5 seconds before, the charge that had built up gave me a hell of a shock. The only way round it was to keep the aircraft earthed with the pole in one hand until the strop was hooked up.
One of the funniest moments was when picking up a package from a site where we couldn't land. We came to a low hover and my crewman leant out the cabin door to pick up the package from a man on the ground. There was a scream from the back as the aircraft's static charge earthed itself. The aircraft had earthed itself across the gap between the crewman's microphone and his lips and then through his body to the man on the ground. My crewman couldn't speak coherently for about ten minutes as he cussed and sweared about the burn on his lips. My ability to hover accurately was totally lost whilst I and the rest of the crew dissolved into hoots of laughter.