Serpo allegedly is the code name of a planet that circles one of the two suns of the Zeta Reticulum Rhomboidalis constellation.

Between November 2005 and April 2011 information was leaked onto the Internet, claiming that the US Government made contact with its inhabitants after a crashed UFO with a surviving crew member was found. In 1965 twelve volunteers were exchanged as ambassadors. (A first attempt in 1964 had failed). They stayed on Serpo for thirteen years before eight of them returned to Earth. (Two died, and two preferred to remain).
The inhabitants of Serpo are referred to as the Eben. It is not clear, however, whether this would be their name, or whether the expression is used in a generic way to refer to Extraterrestrial Biological ENtities.

An anonymous source claiming to work for British intelligence services claimed in 2077 that the real name of the planet was Seinu, and not Serpo.

The name Serpo is also used for the covert project with regard to the exchange of these ambassadors. One source claims the real name of the project was Crystal Knight. As such it belongs to the Aquarius range of covert projects and is also related to the projects Plato and Sigma. (Allegedly, the name of the exchange project was changed to Serpo when the 'ambassadors' returned in 1978).

Inconsistencies in the texts that are leaked on the Internet about Project Serpo create the impression that at least part of the information is actually dis-information, which is to be expected with these kinds of 'leaks'. This is especially the case with the so-called diary of the commander, which is riddled with inconsistencies.
In April 2006, an anonymous source claiming to have been involved in the real project states that most of the information released on the site is dis-information. In May 2006 yet another anonymous source claimed that the Serpo project never took place, and that the information about it was compiled only to deceive the Soviets. Most researchers, however, tend to consider these claims themselves disinformation or speculation.
The bottom line is that at present a lot of claims are being made, and no material whatsoever is being presented by any party to back them up. Yet at the same time, most sources who would know of a Serpo-like programme, do confirm that such a programme did exist, and that the exchange of ambassadors did take place.

In private conversations in October 2022, it was alleged that Serpo was the code name of the exchange project and not the name of the planet. Serpo would have been an acronym for Secret Extraterrestrial Remote Planet Operations.