An Awkward Barmaid Slip-Up

I was at a local restaurant with a group of friends a few weeks ago. I went to the bar

to buy another beer, the barmaid started to pull the beer, halfway through pouring,

the keg rang out, I said its ok, I'll wait while you tap another keg.

However, that was the last of the brand I had ordered, as she was pouring

a new beer, she said "If you like a lot of head, I'll give it to you for free" motioning

to half filled glass. The horrified look on her face as she realised what she had said,

priceless. I didn't understand half of it.