pose as (someone or something)
To present or portray oneself falsely as a different person or type of person. Someone posing as a security guard managed to sneak in and steal a bunch of company secrets. You only studied psychology for a single semester, so stop posing as some sort of expert on the topic!
pose as someone or something
to pretend to be someone or a type of person. I posed as Gerald and got the job. I posed as a nurse and got a job at a summer camp.
pose as someone
to pretend to be someone else. The impostor posed as the president of the company. My twin posed as me while I went on vacation.