My gf's dad still gives me a hard time... for the most part, he forgets. I can convince him one day and then a week later, he still thinks I'm just sitting on my ass and having fun all day.
As soon as he opens his mouth, I immediately swing the laptop around, hand it to him and say "here, you do it then"
The look on his face as he stares directly into the code of a php file is priceless.
At that point I say "Doesn't look like that much fun, does it?"