Momoko Maruyama is a Japanese advertising creator and original character designer, best known for co-creating two notable children's anime series for NHK, Japan's public broadcaster. She frequently collaborates with fellow creator Ryotaro Kuwamoto, with their joint works credited under the name m&k.

Maruyama first gained recognition as the co-creator of Deko Boko Friends, which translates to Uneven Friends. This project began as a collection of thirty-second animated shorts that first appeared on the long-running NHK children's program Okaasan to Issho in 2003. The series features a cast of twelve distinct creatures, each designed to represent different personality traits, likes, dislikes, and quirks. The primary purpose of Deko Boko Friends was to promote acceptance and understanding of people with diverse personalities and appearances. The shorts proved successful enough to be distributed internationally by Viz Media, airing in the United States on Nickelodeon's Nick Jr. block and Noggin, as well as on Treehouse TV in Canada.

Following the success of Deko Boko Friends, Maruyama and Kuwamoto created Zenmai Zamurai, a longer-form children's anime that aired on NHK Educational TV from April 3, 2006, to March 26, 2010. The series ran for 215 episodes, each presented in short five-minute segments. The story follows the title character, Zenmai Zamurai, a young samurai living in a village called Karakuri Oedo during the Edo period. The protagonist has a wind-up key on his head, and his life force depends on performing good deeds, which wind the key and extend his lifespan. He carries a sword called the Dango-ken, which has colorful Japanese dumplings skewered onto it, and he uses this sword to shoot dumplings into the mouths of wrongdoers, making them happy and reforming their behavior. The show's theme is based on the Japanese proverb Ichinichi Ichizen, meaning do a good deed daily.

Beyond her work in television animation, Maruyama is also recognized for designing the mascot character for Qoo, a non-carbonated fruit beverage produced by The Coca-Cola Company. The drink was first launched in Japan in 1999, and the character's name derives from the sound the mascot makes when tasting the beverage.

The recurring themes in Maruyama's work center on inclusivity, kindness, and moral education for young children. Her artistic identity is rooted in creating simple, memorable character designs that convey clear personality traits and emotional states. As an advertising creator, she brings a commercial sensibility to her character design work, crafting mascot-like figures that are both visually appealing and functionally effective at communicating specific messages to a young audience. Her industry significance lies in her contribution to Japanese educational children's programming, with works that have reached international audiences and introduced Japanese design sensibilities to children's media markets outside Japan.