France is a country built upon the foundations of nationalism and ethnic pride. Due to the nation's age and power, its people are very proud and protective of their culture and heritage. However, France and its urban centers are some of the most diverse in Europe. Pure French representation in a Parisen show would not accurately reflect the ethnic makeup of the metropolis. 

Obviously, there was clear thought and effort put into the cultural diversity of this show's cast. Their identities are expertly weaved into the storyline so as not to disrupt the plot while simultaneously bringing significant attention to cultural identities and characteristics that are usually ignored or used to simply score political points in mainstream media. The intent of the show's creators was to accurately reflect and recognize the many faces that make up modern France. 

The show's creator and director, Thomas Astruc, once expanded upon this in a tweet archived on official-ladyblog's Tumblr page:

There is no need for a cast this diverse for a show to be a hit, especially a show for children, whose interest and involvement in media are in no way staked on the inclusiveness and political correctness of what they consume. Nor are political points usually scored through children's media. This decision was out of a desire to diversify French animated television and include oft not seen faces. This decision will pay off, as exposure to different cultures and peoples in any form is integral to forming well-rounded and respectful children who will grow into (hopefully) well-rounded and respectful adults.