This isn't a prank call. The scenario is that John comes over to Jack's with some groceries. He's gonna be housesitting for while Jack's on vacation, so before he takes off John wants to have some breakfast and go over a few last minute details.
This tutorial explains how to export mp3s from a soundboard, create a .bat file that produces a text list of the mp3s, use Microsoft Word to properly format the list for Macromedia Flash, and finally create and code the button itself that will play one of the mp3s at random when it is pressed.