The storyline of Lost stretched over six seasons and had many twists and turns. Many ponderous issues were swept under the rug and forgotten (e.g. why don't we hear much about the numbers or about baby/mama problems in the later seasons?). But a lot more of these interesting details were skillfully woven back and forth through the show, sometimes having episodes explain things from two or three seasons earlier.
How much do we know about how the show was planned out? Did the writers have a plan for the smoke monster being an ancient disembodied man, that when Jack saw Christian in the early episodes it was really MIB, and about his brother Jacob, from the beginning? Did they have the basic existence of and relationship between the Others and the Dharma people figured out? Did they have the role of Desmond marked out from the beginning?
Or did they just randomly come up with crazy amazing ideas for a few seasons and go "Shoot, how do we tie this all together now?" What kind of behind-the-scenes info is available?