While this two cats were playing, a little one behind them sneak in the bushes and disturbed them. Grey cat noticed him and made that look, which I always want to see on a cats face in a photo Cats always want to know what's going on around them, it's just in their nature.
I used to have a cat just like the grey one except it had white socks like the little one. She had 10 litters of kittens before we had to give her up. This makes me miss her so much but brings back good memories