A Midnight Snack Surprise

A colleague approached this man at lunch that invited him out for a few beers after work. The man said that his wife would never go for it, and that she does not allow him to go drinking with the guys after work.
The colleague suggested a way to overcome that problem: "When you get home tonight, sneak into the house, slide down under the sheets, gently pull down your wife's panties, and give her oral sex. Women love it, and believe me, she'll never mention that you were out late with the boys."
So the man agreed to try it, and went out and enjoyed himself.
Late that night, he sneaked into the house, slid down under the sheets, gently slid down his wife's panties, and gave her oral sex. She moaned and groaned with pleasure, but after a little while, he realized he had to take a leak, so he told he he'd be right back, got out of bed and walked down the hall to the bathroom.
When he opened the door and went in, he was very surprised to see his wife sitting on the john.
"How did you get in here?" he asked.
"Shhh!" she replied, "you'll wake-up my mother!"