The mystery train carrying unknown North Korean VIPs to Beijing departed on Tuesday after what proved to be a brief visit, leaving the city awash in rumors that the visitor was dictator Kim Jong-un.

China’s vast army of online censors has been working overtime to block web searches for information about Kim using his common derogatory nickname among Chinese: “Fatty the Third.”

UPI reports that the word “fatty” was banned entirely from Weibo, China’s version of Twitter. Search terms such as “he has arrived” were also blocked. The largest Internet portal in China, Baidu, blocked searches for phrases like “Kim Jong-un visit.”

In November 2016, North Korean officials grew annoyed at Chinese social media users referring to Kim as “Fatty” or using the Chinese phrase “Jin San Pang” to call him “Fatty the Third,” and reportedly asked Chinese authorities to crack down on the insult. It was so common at the time that Baidu searches would auto-complete “Fatty the Third” if users began a search for “fat.”

Amusingly, the North Korean officials implied that Kim did not know Chinese users commonly referred to him as “fatty” and were afraid his feelings would be hurt if he found out. There was a certain hard practical edge to these concerns, as Kim Jong-un’s hurt feelings tend to be accompanied by a great deal of bodily injury in Pyongyang.

There were conflicting reports in late 2016 about whether Chinese authorities humored the request from North Korea and cracked down on Kim Jong-un fat jokes. The Chinese Foreign Ministry declared it disapproved of “referring to the leader of any country with insulting and mocking remarks” but denied that insults to Kim were completely banned. Whatever may have occurred back then, evidently Fatty the Third made enough of a comeback that Chinese censors felt obliged to unambiguously ban it when the corpulent dictator made his rumored visit to Beijing.

The international rumor mill is still trying to figure out whether Kim Jong-un was actually on the train that rolled into Beijing. An official with “deep knowledge of North Korea” told CNN on Tuesday there is a “strong possibility” the dictator did indeed visit China.

Among the reasons cited to support this theory is that it would be unthinkable for Kim’s first meeting with a foreign leader to be either South Korean President Moon Jae-in or U.S. President Donald Trump; if nothing else, a brief stop in Beijing to pay respects to North Korea’s patron President Xi Jinping would seem demanded by protocol.

An alternative possibility suggested by some observers is that Beijing’s North Korean visitor was Kim Jong-un’s sister and “charm ambassador” Kim Yo-jong, who dazzled Western media at the Winter Olympics and holds a sufficiently lofty official title to serve as a respectable emissary to Beijing.

In any event, the diplomatic significance of a North Korean VIP riding twenty hours each way in a train to spend less than two days in Beijing is a matter of debate. Does that suggest relations between North Korea and China are improving, or was the North Korean emissary originally planning on a longer visit? Conversely, would such a short visit—especially if it was not Kim Jong-un riding in the train—provide China with the desired assurances that it still has an important seat at the table in whatever negotiations occur on the Korean peninsula?