Testing with a friend

What David had invented was a Body Alteration Device, or BAD for short.
Though he quickly realized that he could not demonstrate it in front of his wife of daughters. No, the only person he could really test it with was his equally perverted friend, Peter.

So quickly he gave him a phone call. Half an hour later, Peter's car turned up on the street. Quickly the mentioned rang the door bell.
"David?" he asked into the empty hallway.
"Ah, Peter!", he heard his friend's voice, "I am...".