When a big-name movie or television star has their careers referenced during the work itself, it creates a sort of paradox to the audience where the actor as an actor is somehow a different person from that same actor as their current character. If a Celebrity Paradox is in play, the actor-as-character-X exists in Work X, the work itself references Work Y, in which actor played character Y, but the idea that actor-X and actor-Y are the same person is completely ignored (barring As Himself performances).
Normally, Willing Suspension of Disbelief causes the audience to ignore the idea that Spock looks a lot like Leonard Nimoy, but if Star Trek makes a reference to Nimoy's previous works, the paradox comes into play as the audience may start questioning the factual actor's existence in either fictional universe and who played what role in the fictionalized version of the referenced work. They may also start asking if other actors from that work are going to show up.
It's important to note that, if actor-as-character-X exists in both Work X and Work Y, then it is not an example of this trope. Another way to put this is that "character X appears in both" is insufficient; the actor needs to be in a different character role. This disqualifies Sequels and other works set in the same universe where one actor plays the same role. There's nothing strange about such an example anyway; it's a sequel so it makes sense for the actor to reprise the role.
Something else that disqualifies an alleged example is if an actor plays different roles in the same work. One way to put this is that "actor-as-character-X and actor-as-character-Y exist" is insufficient; character-Y needs to be from a different The 'Verse compared to Work-X. Otherwise you've just got internal Consistency and You Look Familiar.
- The Nespresso ad campaign stars George Clooney as Himself and John Malkovich as God. The former never comments on the resemblance.
- This political ad for Bridget Mary McCormack (a candidate for the Michigan Supreme Court) — besides causing Squee! for fans seeing the cast of The West Wing together again — mentions that candidate McCormack is the sister of Mary McCormack. Of course, Mary McCormack played Kate Harper on the show and in the ad... so CJ naturally has never heard of her. Lampshaded by this (at 2:12):
- If the X-Men movies were in the same continuity as Sam Raimi's Spider-Man Trilogy, some of the mutants must have wondered why J. Jonah Jameson was training insurance agents (for Farmers insurance).
- When Bill Watterson interviewed with the L.A. Times about Calvin and Hobbes, he drew this◊ doodle to accompany it (Calvin and Hobbes appear to have no idea who the interviewer is.) More such rare drawings can be found here.
- One Peanuts cartoon has Lucy watching the Rose Bowl parade on New Year's Day when Linus enters, asking "Has the Grand Marshal gone by yet?" to which Lucy replies, "Yeah, you just missed him - but he wasn't anyone you ever heard of!" Naturally, the Grand Marshal that year had been Charles Schulz himself.
- A borderline example from the 1950s: Snoopy is doing impersonations, and Charlie Brown whispers to Schroeder that his dog is going to be imitating "Mssp Msss". Snoopy then squints his eyes and rolls his dog ears up into mouse ears, looking exactly like...Mickey Mouse. ("Frightening, isn't it?" Charlie asks Schroeder.) What's amusing about this is that Charles Schulz was offered a job at Disney early in his career!
- Back when it was still a print publication, Cracked often played with the trope in its annual "summer movie" spoofs; they'd depict characters from one movie taking a break from the plot they were supposed to be forwarding to go to a theater and watch some of the other movies from that summer's lineup, as if they were as "real" as the readers were but the characters in the other movies were fictional. Their Batman Forever parody had Batman, Robin, and various villains going to see other 1995 summer blockbusters, with The Penguin storming out of a Pocahontas parody because he was offended by a scene showing Pocahontas and John Smith eating turkey (because he's a "bird-man," of course). Their 1999 parody of Adam Sandler's hit Big Daddy (or, rather, Big Duddy) started out as a straightforward parody of that movie's plot but then had "Sony" take the orphaned boy to see Inspector Gadget and Mystery Men (or, rather, Inspector Gagit and Misery Men). While watching the Mystery Men spoof, he is inspired to resolve the plot of the main story (social services wanting to take away the boy) by adopting the superhero persona of "Lawyer Man" (complete with a mask and cape), who uses his "super lawyer powers to clog up the courts with meaningless petitions and motions for the next ten years."
- MAD also did these kinds of gags, such as in their 1982 parody Awful Annie, when "Daddy Morebucks" takes Annie to the movies. True, this was a direct reference to a scene in the actual movie being parodied, but here the characters constantly call attention to the fact that they are fictional. ("We'll go from this movie to another movie!" declares Morebucks.)
- Katy Perry's "Waking Up In Vegas" has a rather bizarre version. In the video, Perry plays a woman tooling around Vegas with her boyfriend. They hit a run of good luck, then a run of bad luck. You could reasonably assume that some random woman wouldn't be able to phone up Perry's agent or whoever and ask for more money, but the character actually plays some of Perry's songs on her conspicuous phone, including "Waking Up in Vegas." Complete with album cover. During a poker tournament, the woman's name subtitle reads "Perry." Presumably, the music video for the song hasn't been released yet, or the character hasn't seen it yet, or it's much different from what it is in this world, and the character just happens to be named "Perry" and looks and sounds a lot like Katy Perry. Incidentally, the boyfriend is played by Joel David Moore, from the Bones/Avatar example above.
- Gorillaz has a particular example where they are well aware of their animated nature, actively sharing our universe. You have the many guests that work with them, whose identities are often altered to fit within the band's storyline, but then you have to wonder if these collaborators are that new identity, or if their real persona is somewhere out there. It's even an established fact that their creators Damon Albarn and Jaimie Hewlett are existing people, but aren't referred as such, jarring knowing that Albarn's is the main singing voice behind the band.
- David Bowie's Concept Album 1. Outside plays with this via "The Diary of Nathan Adler", a short story setting up the album's plot and characters (played by Bowie) and "written" by one of them. The album was recorded in 1995 and set in a 1999 where "art-crime" runs rampant; in a brief history of the shocking art (performance and otherwise) that paved the way for this trend, Adler not only mentions Real Life artists such as Chris Burden and Damien Hurst, but notes that in The '70s "Bowie the singer remarked on a coupla goons who frequented the Berlin bars wearing dull surgery regalia..." No first name is given, so this singer may or may not be David (who did live in Berlin for a time in the late '70s)...
- The Beastie Boys' Fight For Your right Revisited features the 1986 Beastie Boys played by Seth Rogen, Elijah Wood and Danny Macbride, their future versions played by Will Ferrell, John C. Reilly and Jack Black as well as the real Beastie Boys themselves as the cops arresting the former six at the end.
- Billy Joel's video for "Uptown Girl" has him playing a mechanic in a ca. 1960 garage who, at the beginning, is watching Joel's video for his previous single, "Tell Her About It", which was represented as having been performed on the The Ed Sullivan Show. So, the video is obviously taking place in an alternate universe wherein Billy Joel is much older than he is in our universe, and would thus probably look much different in 1983.
- Feist's video for "Mushaboom" starts out with Leslie Feist waking up in an apartment and singing along to the song itself on the radio while going through her morning routine. It's ambiguous if this is supposed to be Feist singing along to her own song, or just a fan who happens to look and sing exactly like her.
- In an angle where Shawn Michaels retires from WWE to work in a cafeteria, he uses the pseudonym "Hickenbottom" to avoid attention. Triple H goes on to make fun of the name. Michaels's real name is Michael Shawn Hickenbottom.
- A TNA skit involved Kevin Nash figuring out new nicknames for Jay Lethal. He pitched names like "Vinnie Vegas" and "Oz" which were gimmicks Nash played in WCW at the start of his career. He openly acknowledged this while trying to figure out a gimmick for Sonjay Dutt. ("I wrestled two matches in that one year and earned six figures!")
- As certain wrestling skits over the past quarter-century have established, the characters of Frank Drebin, Arliss Michael, Alex J. Murphy, and Charles Lee Ray all exist as their fictional selves....which gets freakin' weird once you remember that the wrestlers exist in our world as well as their fantasy one, not to mention that Bill Clinton, George W. Bush, and Barack Obama have appeared as well (as lookalike actors playing them, of course, as well as a taped appearance from the actual Obama). Granted, Robocop and Chucky were established in WCW, and may or may not be canon to WWE, but considering that WCW was meant to be in the real world as well... ow, I think I just pulled my brain.
- Also, Tiger Woods is apparently an actual tiger.
- Adam Sandler appeared in the audience at WrestleMania 21 to see Big Show wrestle. I wonder if Sandler asked him for a job again afterward....
- And here's something to truly ponder: Sgt. Slaughter is both a "real" wrestler character and a fictional character in the G.I. Joe cartoon series. Wait....does that mean that the characters in G. I. Joe....actually exist? (And if that's true, why did they look radically different in the 1980s than in the 1960s? Were there some ultra-secret Cold War projects that the Pentagon didn't tell us about?)
- But then the Rock plays Roadblock, despite the Rock being canon to WWE and Roadblock being canon to GI Joe. Confusing ...
- During the Attitude Era, Crash Holly created the rule that the WWE Hardcore Title was on the line 24/7, but constantly defending the title was wearing him out, one match saw him defend the title while doing his laundry. He then hires Shaft to protect him, but never once comments how much he looks like Samuel L. Jackson.
- In the world of Lucha Libre, the legendary luchador El Santo was, during the 1960s, simultaneously a film star, a comic book character, and an active professional wrestler. This bizarre triple paradox also applies to his rival, The Blue Demon.
- In The Gobetweenies, Tom is a huge Doctor Who fan. Tom's father, Joe, is played by David Tennant.
- In Clare In The Community, a Radio 4 comedy series about a social worker based on a comic strip in The Guardian, reference has been made to a comic strip in The Guardian about a social worker, which Clare doesn't find funny. In addition, Richard Lumsden, the actor who plays Ray, was apparently an old schoolfriend of Brian.
- In The Navy Lark, Leslie Phillips' character is a huge fan of... The Navy Lark, especially "that chap who plays the silly-ass sub-lieutenant" (i.e. Leslie Phillips). No other character can fathom his lack of taste.
- In Hancock's Half Hour, Tony Hancock's character has a radio show, but his co-stars don't appear in the in-universe version - except in one episode, where a character played by Kenneth Williams recognises Hancock and Bill Kerr by their voices, because he's a regular listener (he thinks it's mostly rubbish, except for Kenneth Williams!).
- In The Ricky Gervais Show, Karl pitches an idea for a movie about a failed actor who gets his brain placed inside Tom Cruise's body. When Karl is asked who should portray the actor in his original body, Karl suggests Ted Danson. Stephen is quite perplexed about the concept of a universe where Tom Cruise is still a famous actor yet Ted Danson isn't.
- In the Richard Diamond Private Detective episode "Mrs X's Missing Husband" Diamond runs into a woman at a bar who hires him to find her husband who has disappeared. She's pretty vague on the details, refusing to say anything about her and her husband other than that his name is Rick. Reluctantly Diamond takes the case though he suspects that she might be trouble. She has a picture of her husband which analyzed but comes back stating that the man is Diamond himself. Eventually they track the husband to a sanitarium but he was released and she runs and eventually goes to the airport as they were planning on flying out to LA. Later Diamond receives an envelope containing five hundred dollars and a letter explaining that she just found out she was pregnant and that she was going to take a year off from work to have her baby and her husband had a nervous breakdown over the thought of him having to support the two. The letter is signed June Allyson, a Hollywood starlette who's husband was: Richard Diamond Private Detective star Dick Powell.
- In the 1939 play Arsenic and Old Lace, one character is told repeatedly (and to his borderline homicidal annoyance) that he looks like Boris Karloff, who played the part in the original Broadway production. This is Lampshade Hanging in the play, as the part was written specifically for Karloff.
- In a case of works, rather than actors, existing in-universe, RENT is a 20th century adaptation of La Bohème. In the show, Roger plays a strain of music on his guitar and Mark comments that it sounds like "Musetta's Waltz"... which is from La Bohème. One wonders if the characters noticed how closely their lives reflected the opera.
- Well, there IS a song called "La Vie Bohème."
- Older Than Steam: In Molière's play The Imaginary Invalid, which satirizes the medicine of the era, the brother of Argan (the hypochondriac main character) asks him if he would like to see a Moliére play. Argan angrily berates Moliére for making fun of doctors.
- [title of show]. A musical about writing a musical about writing a musical, the musical they're writing being [title of show]. The main characters are all played by themselves, and the musical debuted at the theater festival the characters discuss debuting the musical at. Needless to say, there is a very small window in which this musical works as well as it was intended to.
- Which definitely passed by the time the play was performed by the Arizona Theatre Company.
- The possibility of who plays them after the initial run was addressed in ''the [title of show] show'' episode 6.. Also, in other behind the scenes material, it can be seen that two standbys had been hired.
- In Don Giovanni by composer Wolfgang Amadeus Mozart and librettist Lorenzo da Ponte, Don Giovanni and his servant Leporello divert themselves by singing snippets of opera, first an aria from Una cosa rara by Vincenzo Martini, a colleague of Mozart's who frequently collaborated with da Ponte, then one from Fra i due littiganti by Sarti, and finally Non più andrai from The Marriage of Figaro by Mozart and da Ponte, at which Leporello notes that the tune sounds very familiar. It is believed that this was part also a nod to the audience in Prague (where Don Giovanni was first performed), because in Prague unlike Vienna the Marriage had been a huge success.
- In Evil Dead: The Musical, Annie refers to the Spider-Man film as being "poorly directed".
- Gilbert and Sullivan: Interestingly, true in some cases but not others. HMS Pinafore exists as a fictional play in The Pirates of Penzance ("whistle every tune from that infernal nonsense Pinafore), but King Paramount in Utopia Limited says that he's in touch with a certain Mikado of Japan with some interesting views on punishment.
- The Show Within a Show in The Drowsy Chaperone is said to have first debuted in the Morosco Theatre. When the (real) show went to Broadway, it debuted in the Marquis Theatre, which was built on the same site as the Morosco. They even acknowledge it in the show's dialogue, making it a Mythology Gag as well.