High above ROBLOXia, in space, there is a floating platform. It flies around the universe as a comet as stops at certain planets (ROBLOXia is one), which makes it walkable. When it stops you fight on it with your planet's weapons. Then, one day, it stopped at ROBLOXia. A rocket full of ROBLOXians with ROBLOXia weapons was sent to it.
You were on that ship.