Alter-ego
Some actors working on a project tend to get so invested with their character, in order to perfect it, they have a hard time telling where they end and the character begins. Being invested in your character is important in order to do a good job, but it’s also important to draw the line between acting and reality.
The person tweeting this is on the same page as us. This type of behavior is socially weird; nobody should give that much importance to their alter-egos. Not only that person lost a good date with what seems like someone who knows a thing or two, they got publicly shamed for it. Now, that is one heck of a brag gone wrong.