Call of Duty: World at War (CoD:W@W for the more efficient among you) has defended its number one position on the all-format UK game sales charts, extending its reign to a fifth consecutive week despite heavy holiday competition. Mario Kart Wii took the second spot, followed by FIFA '09 and, still quite bizarrely, Need for Speed: Undercover. Oh, but wait until we tell you what's in the fifth spot. Dr. Kawashima's Brain Training. Remember that one?

Further down the charts, Ubisoft's cel-shaded scurrier, Prince of Persia, climbed to the 20th position while Sonic Unleashed went from 33rd to 12th. We'll let that sink in for a few moments.

This article was originally published on Joystiq.