This writeup was formerly at "Byng-King thing," which is what virtually every student of Canadian political science calls the events herein described. (I only include the word "virtually" to allow for the possibility that there are strange colonies of scholars in, say, Nova Scotia who refer to it differently. If there are, I have never encountered a single one of their emissaries.) I do not know why it was moved.
The last time a Canadian governor general did anything other than exactly what the prime minister of the day told him or her to do -- a watershed moment in Canadian political history. Canadian politics nerds trying to be really clever call the episode the "Byng-King wingding."
In several former British colonies, a governor general represents the British monarch and fulfills the ceremonial functions that presidents do in many republics (the United States, France, and Russia, with their powerful presidents, are notable exceptions). He or she signs bills into law, hosts visiting heads of state, and -- and this is the important thing -- formally invites the leader of a party that wins a parliamentary election to put together a government. In practice, these days, the governor general is appointed by the monarch on the instructions of the prime minister.
It was not always thus. Governors general used to have real power, back in the colonial days. But that power had declined faster than Lord Byng thought.
In 1926, the Canadian prime minister was William Lyon Mackenzie King, who'd been elected with a minority government nine months before. King was depending on the support of the small but doughty Progressive party, largely a farmers' protest party, to govern.
King's government was hit by scandal when the minister of customs and excise was accused of corruption, and the Progressives got skittish. The Opposition Conservatives started accusing the government of corruption even in the prime minister's office, and King started losing votes in the House of Commons. He fired the customs minister, then promptly appointed him to the Senate, which outraged the Progressives further.
The Liberals were facing a parliamentary censure, the kind of thing that forces prime ministers to resign. King went to the governor general, Viscount Byng of Vimy, and asked him to dissolve Parliament and call new elections (figuring, rightly, that Canadian voters would feel the Conservatives were overreacting).
Lord Byng refused, on the grounds that there had just been an election less than a year ago. King demanded that he consult the British government, which Byng officially represented, and Byng refused that, too. So King's cabinet resigned, and left Canada without a government.
The only alternative Byng had was to ask the Conservatives to take over. Committing political suicide -- because the Progressives hated the Tories much more than they distrusted the Liberals, and would never have given them enough support to win any votes in the House of Commons -- Conservative leader Arthur Meighen agreed.
Meighen's government lasted four days, before it lost on its very first vote in the House. He had no choice but to resign, too, and that left Canada not only without a government, but without an alternative. And Byng had no choice but to call the election King had asked for.
King's Liberals won a clear majority, and no governor general ever came close to messing with Canada's elected government again.