1994 Sagittarius Dwarf found.
2003 Canis Major Dwarf found.
Philosopher Immanuel Kant is the first to have suggested the Milky Way might be a galaxy (1775).
UPDATE: The Sagittarius Dwarf has messed with our galaxy twice in the last two billion years and is only ten million years away from striking the southern face of the Milky Way on the third pass through. The dwarf is being stripped of its native material according to telescope data and detailed simulations.