My brother was bitten by an unknown spider this morning and in true male "I'm so tough" style he of course went to work today, then promptly came home in pain and called one of the 'come to my home!' doctors.
What's the first thing the DR asks when he gets here?
Dr: "Now Luke, where do you work?"
Luke: "I'm a sound engineer and an AV technician"
Dr: "Excellent! Now, tell me, what is an MP3 and an MP4?"