Being A Bad Liar - To Be Mocked or Highlighted??

What do you tell your kid when they lie very badly? Do you let them know because it is so absurd or do you let it ride because you don't want them to get any better? This is where I am. My son, for some odd reason doesn't like to keep his head clean; teeth, face, eyes, ears, hair. We are in a constant struggle with teeth brushing and face washing. How can you have orange bits and juice stuck all over your chin and with a straight face tell me that you washed it?!! I mean my fingers literally stuck to his face there was so much on there! Drool lines were making it's way to his ear! However, he is adamant about having washed it. So, being the kind of person I am (the give 'em enough rope...kind of gal) I say well wash it now. So, as I'm handing him his cloth, why is it as dry as if I just took it out of the dryer??!! I hand it to him and say, "and you are still going to tell me that you washed your face?" He looked me straight in the eyes and said, "I just wrung it out really good". ...And that officer is when I blacked out, I have no idea how he ended up over there, honest!