K67
From Tardis Wiki, the free Doctor Who reference
K67 was a meteorite that nearly hit Earth in 2009, threatening to completely destroy the planet. This meteorite was originally going to be to bounced off the atmosphere by Mr Smith.
However, the Trickster intervened. Andrea Yates was alive instead of Sarah Jane Smith. Without Sarah Jane, Mr Smith wouldn't exist, and K67 would then destroy the Earth.
When the Trickster was defeated, Sarah Jane existed once more and the meteor bounced off the Earth. (SJA: Whatever Happened to Sarah Jane?)
