This is the story of a friendship between a small mouse who didn’t want to become a dentist and a great big bear who didn’t want to become a notary. The bear Ernest lives on the margins. His nose is stuffed up and his stomach empty. He searches through the trash for a little something to eat. Just as he is getting ready to shove his mouth full of whatever he can get his hands on, he hears a cry ring out: “Stoppppp!”. The little mouse that he was going to swallow begs him: “If you don’t eat me, I’ll give you what you love most in this world! And it will be better for your health than this garbage.” This is how Celestine, in trying to save her own life, will turn Ernest’s completely upside down. From these unhappy circumstances, a friendship will develop, a friendship that the world of mice (the world down below) and the world of bears (the world up above) will struggle to prevent, in vain: Ernest and Celestine will overcome all prejudices.
Like-minded Ernest, a busking bear, and Célestine, a boho mouse, forge an interspecies friendship and instantly become a cause célèbre in this thoroughly entertaining and slightly demented adaptation of Gabrielle Vincent’s French children’s books. Living in a subterranean labyrinth with her fellow rodents, artsy Célestine (voiced by Pauline Brunner) is pushed into the stodgy family—well, breed actually—business of dentistry. When making a supply run to the surface one day, she discovers the more liberal lifestyle enjoyed by musician-poet Ernest (voiced by Lambert Wilson). After (platonically) shacking up, the kindred spirits are hauled in front of a kangaroo court to defend their friendship.