I did a prank call once on Skype, i used a TF2 heavy soundboard, and called a gunshop somewhere in the USA.
"i -VANT new weapon!"
"What kind of weapon would you like sir?"
"A GUN!"
"Erm, any specific model?"
It went something like that, they found out pretty quickly.
Eventually, i want to do a prank call, and be a character from Superjail.