Little Johnny's preschool class went on a field trip to the fire station. The fireman giving the presentation held up a smoke detector and asked: "Does anyone know what this is?"
Little Johnny's hand shot up and he said: "That's how Mommy knows supper is ready!"
A cop pulls a guy over one night for swerving in and out of lanes on the highway. He tells the guy to blow into a breathalyzer. "I can't do that, officer, I'm an asthmatic. I could get an asthma attack if I blow into that tube."
"OK, we'll just get a urine sample down at the station." "Can't do that either, officer. I'm a diabetic. I could get low blood sugar if I pee in a cup."
"Alright, we'll take a blood sample." "Can't do that either, officer. I'm a hemophiliac. If I give blood, I could die."
"Fine then, just walk this white line." "Can't do that either, officer." "Why not?"