This is not When Worlds Collide, which is to say, a planet or celestial object colliding with Earth on its natural or manipulated normal travels. Someone, usually hostile, decides to poke physics in the eye and teleport an entire planet into our usually highly visible orbit. Destruction ensues, big-time, as once poked, physics starts in with the gravity shifts on several levels. Its usually not the brightest move, even without using Fridge Logic. Previously considered naming it Nibiruportation, for the planet of myth, conspiracy, and doomsday theorists lore. 1 - Transformers G1 and Dark Of The Moon both have the Decepticons do this, with Megatron blocking Optimus by way of the fate of Cybertron if he tries to send it back. G1 Optimus saves both; Movie Optimus makes a harsh choice. 2 - Marvel's Rom Spaceknight has this as the Dire Wraiths' ultimate invasion plan; which ironically gives Rom and X-Men's Forge the opportunity to banish the vast majority of Wraiths in the universe to Limbo, so great plan that. 3 - The Event has this as the season, and possibly, the series' finale, which really makes one question whether the alien leader, whose chosen Earth name means wisdom, has any sophia to speak of.
Hello, Unknown Troper. You'll need to get known to lend a hand here.