Simply put, when a guest star appears As Himself, the characters will be huge fans of the character and gush about them. This can sometimes be extremely jarring if no one in the cast has expressed any interest in this celebrity beforehand and/or they're in unlikely demographic to be a fan. However, this can be completely justified if the characters are seeking out the celebrity precisely because of their fandom.
In addition to story-based purposes, there's likely a behind-the-scenes reason for this as well. Writers don't want to offend their celebrity guest star by acting like they're not universally beloved, and by hyping up the character In-Universe, it makes their guest appearance seem like an even greater deal. Compare Character Shilling, which this may overlap with depending on what the guest actually does. When meeting the guest star, characters mind wind up Starstruck Speechless.
- The Bold and the Beautiful: Bob Barker has appeared on The Bold and the Beautiful As Himself three times since 2002, but it was his 2014 appearance in which he was quite heavily praised: the other characters spent their entire time on the episode talking about what a charitable man he is, his focus on promoting pet charities took up the whole show, and he concluded his appearance by kicking Liam's ass and throwing him down a hill.
- In Community, when LeVar Burton appears, multiple characters claim to be big fans. Justified as the reason he was called was because Troy is such a huge fan that a signed picture of LeVar Burton is his most desired thing in the world.
- The Fresh Prince of Bel-Air:
- In "'Twas the Night Before Christening", Will, feeling intimidated by Carlton's kiddie car gift he's set to give to Nicky at his Christening, sprouts out that he got Boyz II Men to come sing at it. Naturally his aunt is ecstatic that he did so and informs the rest of the family who gush about meeting them, but Will now has to convince the band to come do it for real.
- In "Eye, Tooth", William Shatner is set to be a guest on Hillary's show, Carlton is a major fan of his and gushes about meeting. Will a little indifferent but treats Willain cordially and tries to show him a good time. But Carlton, in his overzealousness, ends up breaking Willams tooth by accident.
- In "iMeet Fred", everyone except for Freddie spends the episode gushing about how funny Fred is. The fact that Freddie dislikes his content is the whole conflict of the episode, and he ends the video being forced to admit the videos are funny.
- In the "iParty with Victorious" crossover episode, Kenan Thompson guest stars. Accordingly, everyone gushes about how awesome and rich he is, especially as its his house they're throwing the party at. It's slightly downplayed, however, in that his role is pretty minor.
- Jane the Virgin: Celebrity guest stars are usually treated this way when they appear As Himself — Paulina Rubio (who appears in season one) is Xiomara's idol, and in seasons two and three respectively everyone is awed at Charo and Gloria Estefan. Writer Isabel Allende also makes an appearance in season four to aspiring writer Jane's delight. Inverted in the case of Britney Spears's appearance in season two; she and Rogelio are apparently nemeses.
- Luke Cage (2016): In "Soliloquy of Chaos", Luke meets Method Man while foiling a robbery and is quite thrilled about it. Method Man is equally in awe of Luke and recounts the story on a radio show.
- In the The Muppet Show, Miss Piggy would regularly do this with any male guest star. Sometimes for special guests like Edgar Bergen, the whole gang would welcome them.
- New Girl. An episode has Prince guest star as himself. The sheer amount of excitement the entire cast has at meeting him is a bit surprising given none of the character's established musical tastes really seem to include Prince.
- The Noddy Shop had a song bragging about how cool the character Jack Frost, who was played by Gilbert Gottfried, was.
- In one of the more shameless examples of this trope, one episode of Royal Pains features a sudden guest appearance by Khloe Kardashian, with Hank's girlfriend enthusing over her, which is especially jarring given that the series usually makes fun of reality TV stars.
- Played with in the Toast of London episode "Hamm and Toast". Pop-culture oblivious Toast had never heard of Jon Hamm before the episode, but the whole plot revolves around how incredibly charismatic Hamm is and Toast's increasingly bizarre attempts to impress him.
- Victorious: In "Ice Cream for Ke$ha", every character is eating gallons and gallons of ice-cream solely to get the chance to meet Kesha, and get very excited when they even learn about the contest.
- V.I.P.: In the episode "Hard Val's Night" Val is hired to protect the members of Lit from a gang that's trying to steal A. Jay's lucky belt buckle. The whole episode has every (female) member of VIP, especially Val, fawning over them, obviously a little star struck, and features a few scenes of women all over them. At the end of the episode Val gets to guest star in the band's upcoming music video, and while they're watching it the female members of VIP debate amongst themselves which member of Lit is the cutest. Out of universe, this is a little justified because Pamela Anderson was already a fan of the band before she had them guest star on her show. Also somewhat Zig-Zagged in the music video at the end of the episode, which ends with the members of Lit rather humiliatingly being hunted down one-by-one and eaten by a 90 ft version of Val.
- Burt Reynolds appears As Himself in an episode of Archer where he is basically The Ace and Archer fanboys out at him. Justified, as Archer being a huge Burt Reynolds fanboy was already a well-established character trait beforehand.
- Johnny Bravo has the episode "Johnny Meets Farrah Fawcett", in which Bratty Half-Pint Suzie is having a birthday party. Johnny declines to attend, until he learns that Farrah Fawcett is Suzie's cousin, and she appears in person to visit Suzie. Johnny is a huge fan of Farrah, being "the only person in the world whose hair is prettier than mine." Johnny goes to ridiculous lengths to attend Suzie's party and meet his idol.
- Parodied in The Simpsons when Jay Sherman from The Critic appears in "A Star Is Burns". When this aired, creator Matt Groening, took his name off the producers credits because he was against the crossover in the first place when Fox requested it, feeling it was a shameless ratings stunt. This joke is likely a reference to that.
Homer: Bart Simpson, meet Jay Sherman, the critic.
Bart: Hey, man. I really love your show. I think all kids should watch it! [turns away] Eww, I suddenly feel so dirty.
- Appears increasingly from so since the 10th series or so, often with characters be announced with "(Profession) (Name)"! Notable examples include Lady Gaga, Michelle Obama (though she is just a soundalike) and Elon Musk.
- South Park:
- It's rare for a celebrity to be play themselves on South Park, but when Robert Smith of The Cure appeared in Season 1's "Mecha-Streisand," the main boys (who are all younger than the band's demographic) all gushed about his music, with Kyle remarking that "Disintegration is the best album ever!" Even Jesus Christ himself refers to Smith as "our savior." Smith also turns into a kaiju and defeats the titular Humongous Mecha version of Barbra Streisand after both Leonard Maltin and Sidney Poiter (neither of whom are voiced by the real people) fail to do so.
- "Wing" features the titular singer Wing, based on New Zealand singer Wing Han Tsang in a rare "proxy" example; Wing's only vocal performances are musical recordings of the real Wing's songs, and everybody in the episode adores her music, with the main boys becoming her talent agents and Sylvester Stallone wanting her to sing at his son's wedding. Parker and Stone really are fans of Wing's singing and listened to it to relieve frustration, so the episode is a love letter to her. Wing approved of the music and her cartoon likeness, and thanked them for the Colbert Bump her music got.
- The Super Mario Bros. Super Show! had plenty of guest stars for the live action segments, and almost inevitably, Mario and Luigi will be avid watchers of their show, consider them an inspiration, or whatever fits for the relevant star's claim to fame.