Why was The Melancholy of Haruhi Suzumiya broadcast out of sequence? When I watched The Melancholy of Haruhi Suzumiya on DVD, the episodes were shown out of order. It was somewhat funny, since in the previews, Haruhi and Kyon argue about which episode number comes next, but other than that, I didn't see the point of it. It didn't have interwoven plot threads, or any in-universe reason to be shown out of order. It looks like in other releases, the episodes were arranged in chronological order, so it must not have been essential to the viewing of the series.

Put simply: Why did The Melancholy of Haruhi Suzumiya have a version that was not in chronological order?
As far as I can tell (and admittedly this is a bit speculative), the reason was to spread out the plot to avoid having the second half be entirely episodic. The creators knew that the main plot (episodes 1-6 in chronological order) would not take a full season (14 episodes), but the next major storyline was not for a while, so they had to insert some episodic content. However, these 6 episodes don't leave much room for breaks, and equally importantly they would rather use canon content from the light novels than make up their own.

So the creators used content from future light novels. This let them intersperse the plot with the episodic material. The 6 plot-related episodes are all in order among themselves, and the others are placed in whatever order the director thought was best (e.g. in terms of character development).

I'm looking for something official to confirm this, but I've had no luck so far. Barring that, this seems to be at least the prevailing opinion of most people on the internet.