After seeing The Package, my friend and I noticed that FST Sun scrutinizes herself in a mirror directly before OT Sun loses her ability to speak English.
If you recall the opening of LA X, Jack does the same before noticing the cut on his neck, then recognizing Desmond.
In What Kate Does, Kate has a lot of bleedover when she is changing after getting her handcuffs off, and she does all this directly in front of a mirror.
In Lighthouse, it appears as though Jack has another weird feeling when he notices his appendix scar, again in front of a mirror.
So it seems to me that the bleedovers occur when they look at mirrors. Or, if you will, remembering how much Alice in Wonderland is referenced in Lost, it is sent Through the Looking Glass.