The sudoku was so confusing and mindnumbing that my brain melted and oozed out through my nose. The brain-ooze happened to be extremely acidic, and burned holes through my chest and legs as it dripped onto them, eventually eroding my heart away. Then, the chair gave way under my weight, and it just so happened that someone had placed a rather large railroad spike under the seat. It ripped through and would have pierced my heart, had it not already eroded.
The extra weight placed on the railroad spike was just enough to depress a long-stuck button that had been accidentally left right under it. The button also just happened to be the remote launcher for over 300,000 nuclear missiles worldwide, launching the earth into sudden nuclear holocaust. The radiation caused the surviving insects to mutate into giant gelatinous monsters, and they began feasting on each other, as well as the few mutated humans who still existed, but were slowly dying of cancer. To stop the feasting and the horrifying deaths that were being caused, the humans used all of the Earth's resources to develop a giant fusion reactor, which they plumetted into the planet's core. Within a few hours, the Earth became the Solar System's second sun, and all life was wiped out on the planet.
The added gravitational pull of the second sun, growing daily by pulling in bits of cosmic debris as it floated by, sent the orbits of the other planets out of whack. With two suns, the orbits became irregular, especially so considering that the smaller sun was orbiting the larger, and planets began colliding. Jupiter and Neptune were sent completely out of orbit and began wandering space freely, while the other planets were smashed into bits, which eventually found their way into one of the two suns.
The increasingly irregular system of orbit between the two stars sent the entire system out of orbit with the galactic core. They moved onward toward the core, eventually being drawn into the gigantic mass at the center. The galactic core gained just enough mass through this to send the entire galaxy out of whack, drawing in every single planet and star within its reach. The entire mass of the galaxy was condensed into one giant celestial mass, great enough that it began to draw mass from other nearby galaxies.
As the other galaxies lost more and more mass, they eventually succumbed to the large mass's gravitational pull, and the entire universe was eventually condensed into one large mass. The mass was extremely unstable, and continued to become more and more unstable until the entire mass exploaded, sending particles to the edges of the universe. Over the course of several centuries, these masses eventually combined, forming stars, planets, and galaxies. On one planet in a tiny system of the new Milky Way Galaxy, the first signs of life sprang up...
Long Story Short: The sudoku made the universe expload. Big Bang #2. Everything dies and the universe starts over.
(Sorry, that might be a little bit much... I got a bit carried away there

The next one will be shorter.)
Go have a great day in which nothing bad happens.