A very loud, unattractive, mean-spirited woman walked into Wal-Mart with her two kids, yelling obscenities at them as they made their way from the parking lot into the store. 
The elderly Wal-Mart Greeter said pleasantly, 'Good morning, and welcome to Wal-Mart. Nice children you have there. Are they twins?' 

The woman stopped yelling long enough to say, 'Hell no they ain't twins! The oldest one's 9 and the other one's 7. Why the hell would you think they're twins? Are you blind, or just stupid?' 

'I'm neither blind nor stupid, Ma'am,' replied the greeter. 'I just couldn't believe someone would sleep with you twice. Have a good day and thank you for shopping at Wal-Mart.