The use of alter egos by the two main characters, Jack and Algernon, drives the plot of the play. Jack uses the alias “Ernest” and, in this way, manages to have his fun in the city without stories of his bad behavior attaching to his real name and ruining his reputation in the country. This strategy backfires when his young ward Cecily turns out to have fallen in love with “Ernest” wholly due to tales of his ill repute. Instead of insulating Cecily from moral turpitude, Jack has primed her to marry a debauched young man like Algernon.

Meanwhile, Algernon invents a whole other imaginary person, Mr. Bunbury, whose frequent illness gives Algernon a pretext to escape his social obligations. Algernon later displays his ease in assuming or discarding an identity by pretending to be Ernest when he shows up to Jack’s country estate.

Both men, then, pretend to be Ernest when convenient, effectively swapping the role depending on their location. This relationship to the name “Ernest” belies the relationship between the men: they are essentially the same person. Since “Ernest’s” escapades, as described to Cecily, are actually Jack’s, Algernon should not be able to pretend to be Ernest so easily unless a rough account of each man’s life in London is indistinguishable.