Recently released on DVD in North America, A Monster in Paris (trailer) is a CGI-animated kids' film that originally came out in France in October 2011 as Un monstre à Paris.
Taking place during the Parisian flood of 1910, the two main characters are Emile, a shy film projectionist and amateur cinematographer, and his friend Raoul, a tinkerer who likes to invent gadgets and operates a delivery service out of the back of his truck. During a late-night delivery to an absent scientist's laboratory, Raoul plays with chemicals, unaware that his tampering accidentally creates a giant flea with a beautiful singing voice.
The "monster" is quickly targeted by Maynot, the Commissioner of police, who becomes obsessed with capturing and killing it as part of his campaign to become mayor. He's also taken an interest in a cabaret singer named Lucille, who disguises and hides the flea after recognizing its musical talents.
Raoul is an old friend/enemy of Lucille's, and soon he and Emile are in on her secret, trying to find a way to protect the flea from the Commissioner.