The Rationalussy Wiki describes the Unexpected Rationalussy Paradox as follows:

Eliezer Yudkowsky tells you that he is going to tweet (or xeet) the word "rationalussy" in 2023, but that the day will be a surprise. More specifically, you will not be able to know what day it is going to occur on until he actually tweets it.

You conclude from this that he will not tweet it for the first time on Dec. 31, since then the day would not be a surprise: You would know as soon as 12/31 midnight comes around that he would be tweeting it on Dec. 31, since he had not tweeted it on any other day, and it is the last day of the year to do it. You therefore buy lots of NO shares in the corresponding market (though not too many - after all, he could tweet "rationalussy" multiple times, with only one of them being on the last day).

However, you then realize that it can't happen on Dec. 30 either. After all, if it hasn't happened by the end of Dec. 29, then you would know on midnight, Dec. 30 that it was going to happen that day, since you've already eliminated Dec. 31 as a possibility. And the same reasoning can be applied to Dec. 29, Dec. 28, and so on, all the way down to the current date. You conclude that what Yudkowsky said is impossible. There is no way he can tweet the word "rationalussy" in 2023 while keeping the day a surprise. So much for being a rationalist! You go about the rest of your year feeling smug about having schooled Eliezer Yudkowski in basic logic.

Then, on Dec. 29, 2023, Eliezer Yudkowsky tweets the word "rationalussy", in a total shock to you, and to the market on the subject. Despite your seemingly valid argument, every part of Yudkowski's original announcement was true. He did tweet the word "rationalussy" in 2023, and you had no idea what day it was going to be until he actually made the tweet, despite being told in advance that he would do it on a surprise day.

We now have markets asking whether Eliezer Yudkowsky will tweet "rationalussy" on each of the last five days of 2023:

/PlasmaBallin/will-eliezer-yudkowsky-tweet-the-wo

/nanob0nus/will-eliezer-yudkowsky-tweet-the-wo-58fbde5fbba4

/ButtocksCocktoasten/will-eliezer-yudkowsky-tweet-the-wo-d79032c3984b

/ArmandodiMatteo/will-eliezer-yudkowsky-tweet-the-wo-d7c0423fe232

/ArmandodiMatteo/will-eliezer-yudkowsky-tweet-the-wo-4ceb54c7287c

And of course, there is the main market on whether he will tweet it in 2023 at all:

/SG/will-eliezer-yudkowsky-write-a-twee

This market resolves N/A if Eliezer Yudkowsky doesn't tweet the word in 2023, or if he tweets it before Dec. 27. Otherwise, it resolves YES if the average conditional probability for the first day that he tweets it on is <50% on the day that he tweets it, and NO otherwise. The conditional probability for each day is just the probability for the market about that day divided by the probability of the main market.

I am using the Central Time Zone to delineate days, so the average will be taken from midnight CT on the day Yudkowski tweets the word to the time that the tweet is actually posted.