Louie's Dark Secret is an unlockable movie in Pikmin 2. It is unlocked by attaining a pink flower on all 30 of the challenges in Challenge Mode, which is done by completing each without a single Pikmin loss.
When Captain Olimar returns from his first visit to the Pikmin Planet, the President tells him that all of the Golden Pikpik Carrots that Hocotate Freight was transporting had been eaten by a Ravenous Space Bunny, resulting in a huge debt which Olimar and Louie are promptly sent back to the strange planet to recover. The truth about the debt, however, is different, and does not involve a ravenous space bunny. The cinematic tells of Louie's appetite being so strong that he was not able to resist eating all of the carrots. In the end, he ate every last one, which lead Hocotate Freight to suffer from the enormous debt. When he returned from his mission, he lied to the President, convincing him that a "ravenous space bunny" ate all of the carrots.