This, of course, makes me want to get bitten and was hoping this community could give me a list of very light spoilers that I might include on the card I will send along with the DVD set. Something along the lines of "the clumsy guy in the pilot's really the villain!". I want to tease her but, at the same time, don't really want to spoil her. Something in Serenity or The Train Job would be preferred simply because it would be out of the way quickly whereas telling her the truth about River in Objects in Space would probably be a bit much.
uptheapples gave the perfect spoiler.