Mr. Yamaguchi is a middle-aged Japanese man who worked as the head of Yamaguchi Industries, an international corporation that's also the parent company for the Reptar-franchise (including EuroReptarLand). During Rugrats in Paris: The Movie, it's said that he was going to eventually step down as the head of Yamaguchi Industries and was in the process of looking for a replacement, and Coco LaBouche was one of the employees under consideration. However, Yamaguchi wanted his successor to be concerned with more than just money--he wanted his replacement to be good with children as well, especially since children are the main audience for the Reptar-franchise. When Coco lied and told him that she loved children and was engaged to a man with a child of his own, this seemed to delight him and he promised Coco that they would discuss the promotion after the wedding.When he learned that Coco was deceiving him, that she actually hated children and that she had the heart of a kid in a jar, he fired her on the spot. Assuming that he still went through with stepping down as the head of Yamaguchi Industries, it's unknown who he ended up choosing as his replacement.
Mr. Yamaguchi first physically appeared in Rugrats in Paris. He had been mentioned numerous times before that, usually by Charlotte, who holds him in very high regard. Sometimes he is described as being part of MegaCorp, other times he is head of a different company that Charlotte wishes to merge Megacorp with. He is an older man, probably in his late 50's or early 60's, given his baldness, dark gray hair and wrinkles. He wears glasses and has a small, thin mustache.
During his video conference with Coco, he is wearing a dark formal suit with a white handkerchief folded up in his pocket. When he attends the wedding, he is seen wearing a men's kimono, geta and tabi.
- The Rugrats occasionally have trouble pronouncing his name, referring to him as 'Mr. Yummy-Guchi' and sometimes 'Mr. Yummy-Sushi'.
- In the episode "Chicken Pops ," he was mentioned to be attendng the Mega Corp-company picnic, and it's implied in that episode that he can't understand English very well, because it's mentioned that at the previous year's company picnic, Mr. Yamaguchi ended up dunking his head into some coleslaw due to a mistake made by the translator. However, in Rugrats in Paris, he's shown speaking perfect English, suggesting that he learned it after the events of the episode.
- Mr. Hasagawa, an associate of Yamaguchi's, appears in the episode Miss Manners. Mr. Hasawaga shares Mr. Yamaguchi's love of children and family.
- "Yamaguchi" basically means "Mountain Mouth" in Japanese.
- In Rugrats in Paris, Yamaguchi was voiced by the late Japanese-American actor Makoto Iwamatsu, better known simply as Mako, who was known for voicing Iroh from Avatar: The Last Airbender (another Nickelodeon show) and Aku, the main antagonist of Samurai Jack.
You can find Mr. Yamaguchi gallery here.