When I was a teenager, my dad was taking me and my girlfriend somewhere and we pulled over to check out the car.
He was complaining of a miss, so he and I got out, opened the hood, and started checking wires and such.
After he'd inspected the ignition a bit, he asked my girlfriend to crank the car.
She did...
...and it bit him.
He yelled out, "Aaaaaahhhh!"
...And she thought she'd killed him.
That happened over 30 years ago, but it still makes me laugh every time I think about it.