On October 14, 2014, over a month after season one concluded, HBO aired the entire season all day as a nod to the date in which the "great departure" occurred in the show.
Season one covers the length of Tom Perrotta's novel 'The Leftovers', the second and third seasons are completely original material.
Justin Theroux's then-wife Jennifer Aniston refused to help her husband with rehearsing lines because she wanted to avoid spoilers. Aniston was a huge fan of the series.
Liv Tyler admitted on an interview given in May 2017 that Meg was such a contradictory and mysterious character that after a while, she started to play her without trying to understand her actions and just performed the scenes as written.
The character of Kevin Garvey in The Leftovers novel (portrayed by Justin Theroux in the show) is the mayor of Mapleton, New York, not the Chief of Police as he is in the show.