Final answer:
The poet mistaken for a conspirator against Caesar in Shakespeare's play was Cinna, who was killed by a mob despite his protest of mistaken identity.
Step-by-step explanation:
The poet mistaken for a conspirator against Caesar was Cinna. This incident is mentioned in William Shakespeare's play Julius Caesar. In the tumult following Caesar's assassination, a mob confuses Cinna the poet for Cinna the conspirator. Despite the poet's claims of mistaken identity, the enraged crowd does not spare him. This mix-up reflects the chaotic aftermath of political turmoil in ancient Rome, where the poet Cinna and the conspirator Cinna, who were different people, were conflated. It underscores the dangerous atmosphere for those even tangentially associated with political figures during times of upheaval.