Crossovers

CLAMP is incredibly fond of crossovers; they even have an entire series dedicated to mixing up their series as much as possible. Gakuen Tokkei Duklyon is crossed over with a few other series and is part of CLAMP's most extensive universe, which also contains CLAMP Gakuen Tanteidan, 20 Mensou ni Onegai!, Tokyo Babylon, X, Miyuki-chan in Wonderland and CLAMP School Paranormal Investigators.

CLAMP Gakuen Tanteidan and
20 Mensou ni Onegai!

CLAMP Gakuen Tanteidan (CLAMP School Detectives) is another of CLAMP's series that came out at the same time as Duklyon. It's three volumes long and is about the escapades of the CLAMP School Detectives, who are also the CLAMP School's Elementary Division Student Government.

20 Mensou ni Onegai! (Man Of Many Faces) is one of CLAMP's earliest works, having come out two years before Duklyon and CGT. It's two volumes long and about the Mysterious Thief 20 Faces, otherwise known as Iijyuin Akira, a member of the CLAMP School Detectives.

CLAMP Gakuen Tanteidan, 20 Mensou ni Onegai! and Gakuen Tokkei Duklyon are all completely intertwined in terms of characters and plot. Akira is both 20 Faces and a member of the CLAMP School Detectives. Imonoyama Nokoru is the leader of the CLAMP School Detectives and the "mysterious" Chief of Duklyon. In fact, the only member of the CLAMP Student Detectives who doesn't make much of an appearance outside CGT is Takamura Suoh.

The biggest corssover in Duklyon is the last chapter of volume one, Kaijin 20 Mensou vs. Gakuen Tokkei Duklyon. In this chapter, the Duklyon boys and the members of the Elementary Division Student Government team up to work in a Joint Dramatic Production Executive Commitee to come up with a play to put on for the student population. Nokoru, being his usual mischevious self, decides that they should have a play where 20 Mensou goes up against Duklyon, and casts both Akira and the Duklyon boys as their respective alteregos (whether he knows about Akira is unknown, but he certainly knows about Duklyon). The boys are all rather shocked by this, but do it anyway.

The play turns into a real confrontation thanks to Akira's mothers deciding that they want Duklyon, meaning that Akira has to steal the boys for them. He does so with the help of a giant dustpan on a plane, and the Duklyon boys are returned after a short visit with Akira's mother.

As all the characters go to the same school at the same time, there are a couple of other brief appearances by characters from other series in Duklyon, and the Duklyon boys make some cameos in CLAMP Gakuen Tanteidan as well.

Both CLAMP Gakuen Tanteidan and 20 Mensou ni Onegai! have been released in English by Tokyopop. The CLAMP School Detectives page is mysteriously missing and the Man of Many Faces page can be found here.

Tsubasa RESERVoir CHRoNiCLE

Tsubasa is the mother of all crossover manga. It started in 2003 and is ongoing, with 11 volumes published in Japanese as of September, 2005.

Tsubasa is about the adventures of Syaoran and Sakura, but not the ones from CardCaptor Sakura. Rather, this Sakura is a princess of Clow country and the childhood friend of Syaoran. When Sakura's memories get turned into feathers and scattered throughout the myriad of worlds, it's up to Syaoran to get them back, with the help of Fye D. Flowrite (a mage trying to avoid his own world) and Kurogane (a ninja trying to get back to his world). They accomplish this with the help of Yuuko from XXXHolic, another of CLAMP's ongoing series.

In their travels throughout the worlds, Syaoran and co. meet a lot of people that look familiar to CLAMP's readers, including the Duklyon boys and Erii. Although these characters may look and act like the ones we know, they aren't the same people.

In chapter 36, the first time Syaoran encounters Kentarou, Takeshi, and Erii, Erii is working as an information seller in the Outo country. The boys are her assistants whose job it is to test the people coming to ask her for information. Erii still wields her mallets with force when the boys do something stupid, though.

The boys also show up in Piffle Country in chapters 72, 80 and 82 as participants in the Dragonfly race. Their Dragonfly is called "Duklyon", too.

An interesting note about Tsubasa: the main artist for the manga is Nekoi Tsubaki, rather than Mokona, who drew Gakuen Tokkei Duklyon. This is what the boys and Erii look like in Tsubasa:

Tsubasa is being released in English by Del Ray Manga, and the page for it can be found here.