A large truck was tailing my son as he drove through town with his girlfriend.  The truck matched them turn for turn, down every street.

My son's concern grew to alarm when the menacing-looking driver pulled next to him at a light, leaned out his window, and glared into his car.  

After a long, hard stare, the man grinned and called to my son, "Sorry, kid, I thought that was my daughter."