After the player have done a certain side quest which involve Tristan and Duke asking who Serenity likes. A new chapter will appear, Lucky will arrive after the player receive the Millennium Scale and show it to Ishizu. Lucky will start barking, this will prompts Joey to think something is wrong and Ishiza will ask them to check it out. When the player arrive at the Kame Game shop, Serenity and Duke will explain that a Monkey Robot came out of the Kame Game shop and that Lucky was talking to it. Duke didn't believe that there was a another person close to Lucky and this cause Duke to realize that the only person who was close to Lucky was Tristan. They explain that Tristan has been turned into a Monkey Robot, possibly due to Reshef's resurrection. If the player talk to Solomon Muto, he will remain skeptical about the situation. When the player talk to Mokuba, he think that is silly, but he remember that they made them and were never sold well. They later donated them to some island. When the player talk to Mokuba again, he will say that they were programmed to behave like monkeys and by showing them, a banana, it becomes excited. Before the player arrive at Galapagos, the three Monkey Robots are excited when they found banana and told the fourth one to leave. When the player arrive at the scene, Joey is shock to see them and Yugi will say that it impossible to find Tristan. The three Monkey Robots are angry and than, challenge the player to a Duel. When the player has beaten them, the player can enter the old building to face the fourth one. By beating the last one, the player enter the Kame Game shop to found out that the Monkey Robot belong to Solomon Muto. The real Tristan come back and will say that he gone to get some food. By beating them, a new chapter will appear. They can be found in the Kame Game shop after this quest, so the player can Duel them again.