More than 3.3 million copies of "World of Warcraft: Cataclysm" were sold within 24 hours of its release, making it the fastest-selling online PC game yet.
The previous record-breaking title was - believe it or not - the previous WoW title, "World of Warcraft: Wrath of the Lich King", which was released in November 2008.
Blizzard is coining it in at the moment. In November, the outfit launched the multi-format title "Call of Duty: Black Ops" which sold 5.6 million copies in its first day on sale.
Cataclysm was released on December 7th and currently tops ChartTrack's UK game chart for PC titles.
"We had to bring Azeroth to the brink of destruction in 'Cataclysm,' but the result was our best expansion yet," Mike Morhaime, chief executive and co-founder of Blizzard Entertainment, said in a statement.
"Call of Duty: Black Ops" tops the UK all-format chart according to ChartTrack.