This paper aims to illustrate the practical application of myth in public life under the early Principate. It begins by sketching the deep historical affection of the people of Rome for the twins Castor and Pollux, and the great posthumous popularity of Nero Claudius Drusus for generations after his death in 9 b.c. Concentrating on the dedicatory inscription of the Temple of Castor and Pollux in Rome, the paper argues that Tiberius Caesar, notoriously addicted to mythology, crafted a potent public association between the heavenly twins and himself and his brother Drusus, and it goes on to examine the effect of that association.