When I was a little younger I think my parents could tell whenever I was masturbating and they wanted to torture me because every time I got going they would call for me.
One time when I was 15 (on my birthday actually) I was in the bathroom pulling on my dick and my dad kept calling me. When he called me for the last time, I was pumping out my cum and I said 'I'm coming dad' at the same time that I actually was 'cumming'. I was laughing when I saw my dad but he never figured out what was so funny.
I did that a many more times and it never got old. My dad never knew that when I said I was coming that I was cumming.