Someone made a Bejeweled clone running as a World of Warcraft add-on:
From the Joystiq article:
The in-game add-on began as a homebrew Bejeweled clone from Michael Fromwiller, cleverly titled Besharded.
Fromwiller developed the add-on as a method of killing time during long
raids and farming sessions, but it wasn’t too long before PopCap caught
wind of the MMO mini-game. Instead of issuing a timely cease and
desist, the casual gaming colossus hired Fromwiller to create a more polished version of the application.
Great move by Popcap.