The 10 Hunter Commandments, from the series itself:
1) Hunters must hunt something.
2) All Hunters require a minimum level of martial proficiency. Being able to use Nen is the minimum level necessary.
3) No matter what may happen, one who has become a Hunter will never have their title revoked. However, no matter the circumstances, a Hunter License will never be issued a second time.
4) Hunters may not hunt their fellow Hunters, except for those who have committed atrocities.
5) Hunters who achieve extraordinary accomplishments in certain fields will receive a star.
6) Veteran Hunters who have received a star, become superior officers and have had their students receive stars will receive two stars.
7) Hunters with two stars who achieve extraordinary accomplishments in multiple fields will receive three stars.
8) If the Hunter in charge does not receive a minimum level of support, then they will have their post removed. In this case, the minimum level is support from the majority of his fellow Hunters. If the seat of chairman becomes open, an election for the next chairman must happen immediately. The vice-chairman is to be left in charge until the new chairman is decided.
9) The chairman decides how the new Hunters are chosen. But in order to make a great change in the existing method, he must not receive support from the majority.
10) Everything not written here is to be decided by the chairman, vice-chairman, and their advisers. The chairman has the right to choose who becomes the vice-chairman and advisers.
Children Voicing Children: The Brazilian Portuguese dub for the movies featured two teenage boys voicing the characters Gon and Killua, who were respectively 15 and 13 years old at the time. Pairo in Phantom Rouge was voiced by a then-13 as well in the dub.
Long rumored to affect the author, particularly the arcs that appeared to be sketchbook work. At least a couple breaks have been confirmed due to a literal physical breakdown causing health issues such as chest pain.
Togashi's comments in the author's section of Shonen Jump in 2016 are downright depressing and sorrowful, with him complaining about being in pain and generally miserable. It's no surprise he went back on hiatus sometime later.
As of 2011, Yoshihiro Togashi has been drawing it for 10 years and is still not finished. It is not a particularly lengthy series compared to its Shonen Jump brethren, but rather, Togashi took so many long breaks, one of which was 15 months, that it has taken this long to make it.
As of 2017, even though the series is not nearly as long as typical Long Runner, it's currently the only other pre-2000 manga besides One Piece to still be serialized in Weekly Shounen Jump, making Hunter x Hunter the second oldest series that is currently in WSJ. If you compare its age with other series running in WSJ, Gin Tama (2003) is the third oldest and every other series premiered in 2012 and later.
No Export for You: Those who want to watch the 3 OVAs (1 adapting Yorknew, the other 2 adapting Greed Island) related to the 62-episode TV series are out of luck, since due to a combination of poor DVD sales of the 62 episode TV series, as well as Viz Media licensing and dubbing the 2011 adaptation (Which not only covered all the content adapted in the TV series, but also covered the content in the OVAs, as well as the Chimera Ant and Chairman Election arcs), Viz has all but officially announced they aren't going to license it.
Tarako voices Melody in a gentle soft spoken voice instead of a cutesy moe-like voice that she does for other characters she voiced.
Matthew Mercer who usually voices serious and/or sarcastic badasses with deep voices, plays Leorio.
Cristina Valenzuela, Erika Harlacher, and Kira Buckland normally provide the voices on several different female characters. Here they portray Killua, Kurapika and Zushi respectively which are considered to be the first time they portray boy characters.
Series Hiatus: Several, leading the more cynical readers to refer to the series as Hiatus x Hiatus. At ~390 chapters to 2019, it would be quite the mental task to determine how long the series would have been without the hiatuses. That is, were it not for this. As of 2020, the series has actually been on hiatus for more of its run than it hasn't.
Troubled Production: The Colombian Spanish dub suffered of many problems during its production: Besides of having a very irregular quality, the script of the dub was plagiarized from a fansub, complete with honorifics and all. Unlike what happened with the other Latin American dubs who used plagiarized scripts (like the Mexican Spanish dubs of the first Detective Conan movies, who where caught red-handed with this), they dubbed the whole first TV series and the OVAs with those scripts with no problems whatsoever with the Japanese licensors, who normally are very strict about using non-official translations for dubs.
Brendan Hunter, the dub actor for Hisoka in the 99' anime, expressed interest in reprising the role for Viz's dub of the 2011 version. Considering his performance was seen as a highlight of that particular dub, it would've been interesting to say the least. Unfortunately, Viz decided to play it safe and cast Keith Silverstein instead.
Togashi mentioned in a discussion after returning from his Hiatus in 2017 that he originally planned for Machi to also get killed by Hisoka, alongside Shalnark and Kortopi, after his fight with Chrollo. Togashi decided to leave her as a survivor because he felt the narrative would have better stakes if she returned to the Phantom Troupe as a messenger.
Reportedly, Studio Madhouse had originally planned on making the 2011 anime a 26-episode seasonal anime, hence the 2 recap episodes early onnote presumably, this would've accounted for the constant hiatuses, so assuming Togashi wrote content whenever the anime was in between seasons, they would've been able to avoid filler as much as possible. However, they eventually decided to make the series a long-runner, resulting in the finished project.