Try:
"I have to work late.....again."
"I'll drive the babysitter home....don't wait up."
"Your sister needed me to help her move into her new apartment. That's why I have a key."
"Mother Superior needs me to unclog some backed up pipes in the convent."
'The nurse from the sperm bank lets me make donations at her house."
"Your mom is just teaching me yoga."
"I only do it for you! If I only spend the night with twins, I can't ever be alone with another woman!"
"I don't remember anything! Who knew a brothel served such strong drinks?"
"I bought a hundred boxes of cookies! Who knew that Girl Scouts earned a badge for personal customer service?"
"My Sunday school girls wanted to learn about the Second Coming, so I demonstrated it!"
DO NOT USE, "I forgot to tell her I was married." It's an instant Game Over!
Cheers!