Rural emergency!

Walking into town I decided take the lower path through the woods but at the last moment chose to stick to the upper track between the fields - luckily for this ewe because through the hedge I spotted her stranded on her back. Sometimes when sheep lie down or lose their footing they roll over and the weight and density of their fleece means that they can't get a purchase on the ground to right themselves. The technical term is 'cast' (another term of Norse origin is 'riggwelter'.) Cast sheep cannot expel gas from their rumen, and their lungs will eventually become crushed, leading them to die of suffocation within a few hours.

I climbed over the fence to run to her assistance. She kicked and struggled helplessly as I approached. "Ewe are in a state" I said, "it's lucky for ewe that I happened to be passing by." I rolled her back on her feet and she ran off without so much as a "Thank ewe!"
(See her rejoining the flock here.)

So, if you see a sheep on its back waving its legs around don't assume it's having fun - it's actually in mortal danger. Waste no time helping it back up or report it to the nearest farm: it's an SOS to Save One Sheep.