Mmm I have done that, came home to hear my wife fucking her boss, I stood outide the door and wanked as he filled her slutty sweet pussy with his cum. I fucked her later that night, she didnt know I knew, her pussy was wet and sweet.
I had something similar happen to me years ago, I can home early and saw my neighbor balls deep in my wife through the bedroom window. Instead of walking in and jerk off watching them. (which I did find exciting) I took some pictures of them through the window, walked over to his house, showed his wife the pictures, then proceeded in fucking the living shit out of each other. Imagine his surprise when he came home to find his 6 month pregnant wife spread eagle on the bed with a thick load of my cum running out of her now well fucked pussy.