We are made to imagine what it would be like to have more than one personality in our head, presumably vying for control.

Notes:
This theme is typically used in fantastical scenarios where the clinical condition of multiple personality (aka. dissociative identity) disorder is not sincerely featured but distinct personalities nevertheless inhabit the same body. As a rule of thumb, it is used when at least one of the personalities at least some of the time is aware of its own condition of having multiple personalities.

Examples:
Norman Osborn struggled with his deranged alter ago the Green Goblin in "Spider-Man" (2002).

Aliases:
what if I had a split personality

References:
https://en.wikipedia.org/wiki/Dissociative_identity_disorder