Celestine is a mouse who lives underground with the other mice. But unlike the other mice, she's not afraid of the bears who live up above. When she's trapped above on an expedition to collect teeth (mice like bear teeth), she meets the bear Ernest and they slowly become friends.
The animation has the look of hand-drawn watercolours, which is the media Celestine herself works in whenever she gets a chance, and it looks pretty good. The ideas are reasonably clever and the dialogue quite funny: it's a fun movie.