How to scare a child and yourself.
Step 1: Grow a beard.
Step 2: Grow old . . . approximately twenty years older than said child.
Step 3: Contemplate some general unfairness of life that you realized during twenty years you were waiting to grow old, such as why people die, having to work for a living, or why adults can't wear pajamas with feet and a big zipper in polite society.
Step 4: Whisper said truths in child's ear, then make a large clapping sound in the child's other ear.
Step 5: Double check child is crying. If not, repeat until desired effect is reached.
Step 6: Feel horrible about yourself and what you've become.
Step: 7: Resolve to get younger, never die, quit work, and buy new pajamas.