My parents came across a Japanese tourist who'd run out of water cycling across the Nullarbor. They filled his '1L' water bottle for him.
The funniest thing I've seen was a poor woman's naked bum. We were winding our way through El Questro Gorge, and me being a straggler was well behind everyone else. The rest of our group had made it to the half way swimming hole, so the middle aged couple that were already there decided to leave. The wife stripped naked to change out of her wet gear as her loving husband held up the towel to protect her modesty from the group, but they seemed to have forgotten the gorge behind them, so everyone walking into the narrow gorge got a surprising show as she bent over to put fresh underwear on
We didn't let on that we'd seen, and they travelled on none the wiser