I was out mowing the front lawn once, and to a casual glance there would also have appeared to be two lads out in the street playing tennis.
What was actually happening was that as I walked up and down the lawn, these two kids were sidling up and down the street so that one of them could hit the ball at me on the pretext of hitting it across to his mate. After a few minutes of the ball whistling past my earholes and bouncing off the lounge window, it fell on the lawn at my feet.
I picket it up, put it my pocket and carried on mowing the lawn, and after a few minutes one of them sheepishly came over and asked for it back. As I took it out of my pocket he flinched, expecting to get it thrown at him, but I just dropped it on the pavement and told him that I'd stick it up his arse if he didn't stop using me as an Aunt Sally.
A few years later, when a new neighbour moved in next door, the first topic of conversation when he introduced himself was about whether I give kids their balls back. He kids never come round to ask for theirs when they come over the fence, so I'm obviously the miserable old git at No. 35 who won't give kids their balls back.