In 1982, Tommy Tutone released one of the best love songs of the 80's, 867-5309 Jenny. The song has provided musical inspiration for aspiring independent artists, a ton of money for Tommy Tutone (but not enough to keep him from getting a job as a music teacher in Iowa), and a random number for a whole bunch of losers to prank call. Please read this ENTIRE ARTICLE if you wish to call for "Jenny", the way i learned what I should and shouldn't do was less than pleasant and nobody should have to make the same mistake when an entire article about the subject is on Instructables.
Step 1: Calling
In my area, the chic gets really annoyed when you call. Somehow she found a way to track her prank caller down (I'll always miss the part of my hand that I lost fighting "Jennny"). That being said, it may be best to use a pay phone. Try to make yourself as impossibly anonymous as possible, and hope that you don't call someone's cell when they're standing right next to you. In a study in the past, most instances of 867-5309 did not exist, so you may have to try a few area codes. If you're really crafty, you can try to find the area code for Willits, Calafornia, as that was the place that Tommy Tutone was based when Jenny was released and you may be calling the real person.
Step 2: Talking
This is the hard part. You may want to request speaking to Jenny, or perhaps simply playing the song loud enough to be heard by the answerer if you get nervous. My father, who prank called Jenny when the song was actually popular, simply sang some of the lyrics from the song. Don't freak out, it will completely ruin the effect.