Basic Trope: A ruse to protect a character's Secret Identity by showing both character's identities in the same place together at the same time.
Alex records a video of himself as Emperor Evulz and plays it to the people of the world claiming it to be live, while Alex makes a personal appearance in front of the people he wants to fool.
Alex hires Steven to dress up as Emperor Evulz and crashing a high profile event which Alex would be attending as himself.
Exaggerated: Alex hires Steven to dress up as Emperor Evulz, and then hires Daniel to dress up as Alex, and Alex will dress up as Steven's secret identity, Captain Good, while a robot is made to look like Steven.
Alex shows a photograph of himself with Emperor Evulz.
Alex has successfully pulled this ruse in the past, so people take it for granted that he and Evulz are separate people.
Justified: Alex wants people to think that he and Emperor Evulz are separate people.
Inverted: Alex crashes an event as Emperor Evulz and Steven impersonates Alex.
Subverted: Charlie quickly recognizes that this is not the real Emperor Evulz who just crashed the party.
Double Subverted: ...and yells "I didn't know this was gonna be a costume party!"
Parodied: Emperor Evulz's costume does not include a mask nor any form of identity-concealing device whatsoever. Yet Alex still feels the need to pull this trick... and it works.
Zig Zagged: Alex is trying to accomplish some goal which only he can do, due to his specific skillsets/powers. Therefore he and the imposter Steven must keep leaving the room and switching costumes, back and forth, over and over, to uphold the pretense.
Averted: Alex and Emperor Evulz are never made to appear together.
Enforced: Alex's attempts at Clark Kenting are patently pathetic, leaving the impression that someone must be onto the secret; this is the writers' solution to those concerns.
Lampshaded: "Y'know how we always point out how you and Emperor Evulz are never in the same room at the same time? Can't say that anymore."
Invoked: Alex constructs the plan to fool Charlie, who is getting a little too nosy lately.
Defied: Alex doesn't care if anyone finds out he is Emperor Evulz.
Conversed: "It's like those times when Batman or whoever would dress someone else up in their costume just so their secret identity could appear in the same place with them... you'd think people would catch onto that little trick after a while."
Played For Laughs:
Charlie is the only person who doesn't know Alex is Emperor Evulz, and so Alex and Steven put on this elaborate ruse for his benefit alone — while everyone else reacts with bored disinterest.
If Steven is impersonating Alex while Alex is Emperor Evulz, people may tell Evulz "Your Costume Needs Work", while they compliment "Alex" on his unusually impeccable grooming.
Alexandria is Emperor Evulz, and Steven has to impersonate her.