Authors have psychic links with alternate dimensions. When they have ideas for things, it’s their connection kicking in, providing somewhat of a live feed/flashback of the events in that alternate universe, which they then write. When an author has a block, it’s because the events haven’t occurred yet; or if they’ve written something that just doesn’t feel right, it’s because the link has weakened and they got the gist of events, but haven’t recorded it properly because the linkened wink has clouded their ability to see the events in full.
Multiverse Muse Theory
Kat is so fricken awesome, go follow her.