Yin Yang Norn
Unfortunately, the two starter norns originally made by Muppetboy have a reaction that makes IV Antioxidant decrease Aging, rather than the other way around, as in all other norns. This was intended to make their lifespan easy to control, however, when downloaded, there is an amount of Antioxidant in their bloodstream, and so the original two tend to die in the space of less than half an hour. However, if you gengineer the Antioxidant reaction back to normal, they will live normally.
Also, when they reach the elderly life stage, they will die immediately, this can also be gengineered out of the population.