Definitions of alter ego
a company used by a person to carry out personal business, and so exposing the person to possible personal liability
Trouble usually follows those who ignore corporate separateness and operate a subsidiary (=a company that is owned by another company) as an "alter ego" or "agent."
a person's second or alternative personality
Becoming Batman (2008) looked at how far advanced training and discipline could transform a regular person, such as Batman's alter ego Bruce Wayne, into a superhero.