advocate agent alter ego alternate alternative amicus curiae analogy attorney backup backup man champion change changeling comparison copy counterfeit deputy double dummy equal equivalent ersatz exchange executive officer exponent fake figurehead fill-in gate ghost ghostwriter imitation lieutenant locum locum tenens makeshift metaphor metonymy next best thing paranymph personnel phony pleader procurator proxy relief replacement representative reserves ringer second in command second string secondary sign spares stand-in sub substituent substitute substitution succedaneum superseder supplanter surrogate symbol synecdoche third string token understudy utility man utility player vicar vicar general vice vice-president vice-regent vicegerent