Featured in Tenchi Muyo! GXP, the Unko (運呼, うんこ) was the flagship of the Good Luck Fleet, created by The Daluma Pirate Guild, captained by Seiryo Tennan.
History
The pirates of the Galaxy were being decimated by the Decoy Division of the Galaxy Police, after effectively utilizing the bad luck abilities of Seina Yamada. So General Daluma decided to fight bad luck with good luck and developed a fleet of ships that employed lucky items to increase the luck of the ships. While Seina was taking a short vacation on Earth, the fleet was deployed and immediately found great success, even succeeding in escaping the Mikagami and Seto Kamiki Jurai's entire fleet, something that had never happened before. Unfortunately for them, as soon as Seina joined the fight, the fleet was unable to counter Seina's extreme bad luck and the fleet was crippled and sent into retreat.
Instead, General Daluma decided to focus on building a flagship that consolidated the most lucky items that could be found and man the ship with the luckiest crew. He contracted the Tennan Conglomerate to create and gather lucky objects, which brought the cooperation of Seiryo Tennan, previously a prisoner of the Daluma Guild. Holding duels to find the luckiest person to captain the ship, Seiryo was able to defeat Tarant Shank. He temporarily lost his captain position in a round of Janken (Rock-Paper-Scissors) to Alan, Barry, and Cohen but they were wasteful of their ship's budget that they begged him to take over (the position and the debt they created).
The GXP novels also reveal that around this time Tarant Shank had fallen to such a lowly position that, in order to stay in the good graces of the Daluma Guild, he had to surrender the blueprints of the Shank Guild's legendary Daidalos ship and the flagship would be their first ship utilizing the design.
When it came time for naming the ship, Seiryo insisted on using a name that included "Luck" in its name, however, seemingly every "Good Luck" name had already been taken in the Galaxy's ship name registry. The only one left was Unko (運呼, うんこ) which could mean "Luck Bringer" in Japanese, but is also a Japanese homonym for the word, "Poop" (うんこ). Others tried to warn him of the double meaning but he refused to hear them. So, even though it was one of the greatest known ships in the galaxy, many pirates were too embarrassed to join the crew.
Other than Seiryo and the three idiots, Kyo Komachi and Maya were also included on the crew.
The ship did prove extremely effective though, easily capturing cargo ships, defeating any fleet and even forcing Seina, Fuku, and the Kamidake to retreat. Combining the Kamidake with the Mikagami sent the Unko into retreat but it wasn't until the Kamidake was combined with the more compatible Mizuki that it seemed that the Unko would meet its match. However, the combined ships instead made a random jump to the location of the headquarters and flagship of the entire Daluma Guild, the planetary-class ship, the Great Daruma. While The Kamidake was single-handedly defeating the big ship, the Unko found itself unable to jump to the aid of their fleet. A member of the crew (Maya, in the novels) noted that the ship was too lucky to jump into such a tough battle and Seiryo recklessly decided that he should eject just about every lucky item on board. But instead of reaching the Great Daruma they jumped straight into another fleet of GP ships and were barely able to escape, suffering extreme damage.
In order to capture the Unko, Seto taunted Seiryo into a personal duel with Seina. In the anime version of events, Alan, Barry, and Cohen gamble and lose the ship betting that Seiryo will win the fight. In the novels, the three guys are also left in command, but Alan and the others have fallen out with each other and it is Alan alone that gambles away the ship while alone on the Racepshi (the location of the duel in the novels). It turned out to actually be a con run by Seto and it was Kuis Panta that came to claim the ship. Barry and Cohen remain faithful to the ship and refuse to leave, as it's their only way to clear their debt. Instead, Kuis offers to pay their debts and employ them herself (Alan runs away with a Recepshi hostess).