This is where the "prank" part comes in.
You walk in very serius, NOT all "Gigglesfest" and you stand in front of the clerk, contemplate momentarily, or rather, give the illusion of thought in your menu choice, and say, "I'll take the Colonel's Chicken Fun Pack."
If all goes well, the clerk will be left in a state of confusion, questioning his or her manger about the non-existent food item you ordered.
In performing this skit, be prepared for strange looks, and dumb questions.
Dane : *walks into KFC* I'll take the, um...Colonel's Chicken Fun Pack.
KFC Employee : Excuse me?
Dane : The Colonel's Chicken Fun Pack.
Employee : Do you mean the laptop pack?
Dane : No.
Emlpoyee : *dumfounded* Was that a limited time offer?!
WHAT YOU DO NOT WANT TO HAPPEN:
Dane : Can I have the Colonel's Chicken Fun Pack?
Employee : That is NOT on the menu.