If the Skyrim prank didn't tip you off, calling people using a soundboard of a video game character is a popular trick. While funny, the prank works best when the person on the other end plays along -- like this guy from a magic shop does when he receives a call from Dota 2's Anti-Mage.
Lots of props for being a good sport there, although you've got to think: this is a magic shop. Surely this call from HattonGames is not the most ridiculous one this guy has received?
Antimage Calls a Magic Shop (Dota 2) [HattonGames]