Old Shame/In-Universe

Anime and Manga

Referenced in Excel Saga: In the opening to one episode, the production staff of the show confront Rikdo Koshi (the writer of the original manga) and toss down several doujinshi in front of him, causing him significant embarrassment. Those doujinshi are actual ones Koshi wrote before he did Excel Saga. Guess what the plot of that episode is based on?
In an episode of Lucky Star, Hiyori invites friends over to her house, only to be horrified when she finds them skimming through old sketches in her artbook.

Comics

Drama Con: When Christine presents Lida Zeff a copy of her first published work to autograph, Leda's reaction is something akin to a brief Heroic BSOD, followed by her putting on the puppy dog eyes to persuade Christine to Kill It with Fire.

Film

In Music and Lyrics, Alex Fletcher openly concurs with the general critical consensus that his only solo album was, in the words of what was apparently the kindest review, "a crass, contrived effort not fit for a dentist's chair." When Sophie reveals she's bought and listened to a copy, he immediately produces his wallet to refund her.
This trope is part of the plot of Notting Hill, where the female lead is a movie star whose pornographic past turns up in the press halfway through the movie.

Literature

In Lois Lowry's Anastasia series of children's books, the eponymous character's father is a literature professor who has published three poetry collections. In an invocation of the trope that authors always think their early work is terrible, he is so embarrassed by the quality of the first collection that he tries to discourage Anastasia from reading it.

Live-Action TV

In Angel a dream sequence reveals that Angelus attended Barry Manilow concerts. It's too much for him, and he's practically begging for someone to kill.
Bones example: Medical Examiner Camille "Cam" Saroyan appeared in a low budget, very cheesy vampire movie called Mother Suckers to help pay for medical school. Upon learning this fact her co-workers of course track down a surviving copy to see just how bad it really is (much to Cam's embarrassment).
In Castle; Richard Castle joins the murder investigation in the pilot episode partly because his curiosity is stoked over why the killer decided to base his murders on Castle's self-described 'lesser works' rather than his later, better ones.
- Despite not being involved in the creative industries, Detective Beckett also has an example, curiously involved -- it involves photos of a shoot during her short-lived career as a model when a teenager.
In Community, when Jeff and Annie are running for student government president, Annie brings out Jeff's audition tape for The Real World: Seattle. It begins with him singing a parody of George Michael's "Faith", "Gotta have that Jeff, Jeff, Jeff".
iCarly: The Benson family, with the sport of fencing.
House discovers Wilson starred in a student film that was later turned into a porno by adding sex scenes from another actor. This is quickly spread to the entire hospital, and House replaces Wilson's usual movie posters with posters from the porno.
I the Robin Sparkles "Let's Go to the Mall TODAY!" tape from How I Met Your Mother. It also has a sequel,Sandcastles In The Sand.
- Similarly, the breakup video Barney made for Shannon back when he was still a hippy
In Party Down, Henry is constantly reminded of his role in a series of beer commercials by party guests recognizing him as Hey, It's That Guy!. Again, he is embarrassed when Casey recognizes him from an old indie movie in Steve Guttenberg's collection.
In a 3rd Rock from the Sun episode, Mary discovered a thesis she had written years ago and which she had thought was brilliant at the time. She read it again only to find it was crap.

Music

"'Fore She Was Mama" by Clay Walker. The narrator recalls finding a box full of photographs that show his mom as a rebellious, notorcycle-riding, marijuana-using wild lady, and is incredulous that she used to be such a person. He and his brother tease her about it, and she ends up burning the box.
Invoked by the Chely Wright song "Back of the Bottom Drawer", which is about a great deal of detritus gathered from former boyfriends, such as stolen hotel keys, napkins with poetry on them, et cetera.

Video Games

In the PC game of Where in Time Is Carmen Sandiego?, the entire plot revolves around a convoluted plot by the title character to erase her history as an ACME detective.

Web Comics

In Sinfest, Monique discovers her old poetry. Then, she disposes of it, she thinks.

Web Original

Strong Bad of Homestar Runner refers to his first attempt at drawing a dragon as the "S-is-For-Sucks" Dragon.
- However, in the Trogdor's 5th birthday toon, he sings a song about the S is For Sucks Dragon, then indicates that he's sick of Trogdor, claiming that "you Internet types" ruined him.

Western Animation

In one Kim Possible episode, Kim blackmails Shego into helping her defeat a villain by threatening to reveal that she used to be a hero.

Kim: Because if you don't help, I'll tell the world that you used to be a good guy.
Shego: You wouldn't.
Kim: I've got a website and I'm not afraid to use it.

Shego: Ugh, my reputation would be shot!

On Phineas and Ferb, Linda Flynn has mixed feelings (mostly embarrassment) about her short-lived career as a pop singer, Lindana, back in the eighties.
In Slacker Cats it turns out Mrs Boots had done some "mistakes" as a kitten like dressing up as a pirate and a fireman in "Cats Do the Cutest Things". Eddie and Buckley blackmail her with it.
In Total Drama World Tour, Sierra brings up Chris's earlier career(making bad movies about talking cats, being on a cooking show that lasted one episode, and being in a boy band). Chris is not amused, to say the least.