You may be disappointed to learn that this is not, in fact, the long-unawaited reboot of the late Jim Varney's classic countrified caricature - if you think I jest, be aware that there were plans at one point to make Son of Ernest - but an animated adaptation of a series of French children's books. In a nutshell: a mouse and a bear are friends.
Yes, that sounds terribly simple. And if the movie were as basic as the picture books, it probably would not work for anyone over the age of 5. But directors Stéphane Aubier, Vincent Patar and Benjamin Renner are trying to make a movie for everyone here, and have fleshed out the world of the characters in some nicely creative ways. The bears now all live above ground, basically acting like people but with some added sleepiness come winter time. The mice live underground, in a Dr. Seussian world, where they carve out everything with their teeth, and as such value dentistry above all else. Frequent missions to the surface to steal the teeth of bear children has led to a tooth fairy myth springing up around them; in the meantime, mouse children are terrified by tales of the Big Evil Bear who wants to eat them.
Celestine (Pauline Brunner), for some unknown reason, believes bears and mice can be friends, and during one of her tooth hunts, she has the chance to put this to the test, as she narrowly avoids being eaten by the broke and hungry one-man-band bear Ernest (voiced by Lambert Wilson, the Matrix sequels' Merovingian) - directing him instead to an easily accessible candy store. Said store is run by a duplicitous bear whose wife is in the dentistry business, so he sees it as his job to rot children's teeth...while Celestine, when she sees the wife's tooth store, sees it as her job to plan a heist, with Ernest's help. When things go wrong, however, they end up having to face the authorities from opposite worlds - Ernest goes to mouse court (man, that sooo should have been a Jim Varney movie title), while Celestine must face a bear judge.
Thematically, there's a lot here that's consistent with the messages of much kid-lit - it's okay to be different, you don't have to be what your parents want you to be when you grow up, and people who aren't like each other can still be friends. But it's the simpler things that are more likely to resonate - what kid won't appreciate the tribute to the primal joys of drawing, and having a parent put that drawing up on the wall? None of this is overplayed for sentimentality, because it doesn't need to be. Children are smarter than that.
As for adults, there are clever sight gags like the mice using mouse traps as bench-press machines, or the convoluted series of boom tubes their dentists use when it would be easier to simply hand the tooth to somebody standing nearby. It is perhaps not a lot to go on - this isn't the kind of cartoon to throw in grown-up references just to make parents feel smart, but it does work hard not to be unacceptable to them either. GKids is releasing the film later this year - I'm not going to tell you it's a must-see, but it is a charmer.