Every year since season two of The Simpsons, in 1990, the series has done a Halloween special, which is not part of the show's normal continuity. The episodes have been called "Treehouse of Horror" ever since the thirteenth special, in 2002, a fact that I learned in 2020. I could have sworn they had always borne that name, but for the first twelve, they were simply called "The Simpsons Halloween Special." I suppose I must have been aware of the older title before the switch, and probably remembered it at least for the first year after the switch, but long before 2020 I had completely forgotten, so I was very surprised to rediscover the old title.
These special episodes may air anytime from the first week of October through the first week of November, so it's important to check the schedule at least a month in advance, if you want to be sure to see it. (I mean, in case you don't already watch every episode of the regular series.) Anyway, the Treehouse episodes will have at least three segments, maybe an extra one before the opening credits, and of course the opening credits themselves will be specially modified for Halloween. Same with the closing credits. And usually, if not always, at least one of the segments will include aliens called Kang and Kodos, either in a major role or a small cameo. Um... I suppose I couldn't possibly have seen the thing when it first started, because I didn't have FOX at the time. I may have seen some of the older Treehouse episodes in reruns, years later. Or not, I forget. And I don't remember which episode was the first one I ever saw first-run. But at some point I decided it should be a tradition to always make sure I watch each new Treehouse episode every year (even in years where it might be the only Simpsons episode I watch that season).
I started this page sometime after Halloween in 2013, thinking that someday it would be nice to rewatch every episode and write a review here. But every year since 2003, I had written at least a little bit about each year's episode in my Halloween journals. And in 2014, I decided I might as well copy and paste those descriptions to this page. I made my first full entry here in 2014, while watching that year's episode, and continued to do so in the following years. Then in 2020, all the old episodes became available on Disney+, so I finally started re-watching them from the beginning (in some cases seeing episodes for the first time), and writing up full reviews. They're still fairly short reviews, though some of the old stuff taken from journal entries will be replaced by new reviews.
Note: Segment titles where Kang and Kodos make an appearance, whether playing a main role or just a cameo, will be lawngreen.