This is when a series celebrates a milestone or anniversary that relies primarily on references to or even the entire plot of the first installment. May or may not be justified in-universe. Similar to Book Ends, except the series hasn't ended.

Comic Books

• Detective Comics #387 (the 30th anniversary issue) and Detective Comics #627 (the 600th issue since Batman showed up), both contained updated versions of "The Case of the Chemical Syndicate", the first Batman story from Detective Comics #27.
  • The covers of the respective issues also homage the original--#387 shows Batman holding up the first issues of Detective Comics and Batman while asking Robin if he's ready for another thirty years, while #627 is a little more direct.
• The Incredible Hulk #393, another 30th anniversary issue (pictured above to the right of issue #1), revisited the site of Banner becoming the Hulk, and answered the question of what happened to Igor Drenkov, the undercover Commie agent who didn't call off the test explosion of the gamma bomb when Banner ran out onto the field to rescue Rick Jones. The cover was also an homage to the first issue's cover.

Live Action Television

• The Doctor Who 25th anniversary season opener "Remembrance of the Daleks" took place the day after the first story, and features the return of the Foreman junkyard and the Coal Hill School. Ace notices a book Susan left behind, and we nearly see a BBC ident advertising the show's premiere.
• The Colbert Report's 100th episode saw the return of the show's first guest.
• Jeopardy!'s 3,000th episode's first round features the clue categories from the first episode.
• Grange Hill opened its 26th season with a new batch of first year students...who all bore vague similarities to the first year students of its very 1st season, including their names and general behavior. Plotlines and characterizations diverged significantly after that first episode, however.

Video Games

• Castlevania: The Adventure ReBirth was released on Wii Ware in Japan exactly twenty years after the release of the original Game Boy game, retelling the story of Christopher Belmont using design decisions that were more consistent with the rest of the pre-Metroidvania series. And putting Death back in.
• For Sonic the Hedgehog's 20th anniversary, he's teaming up with his past self (as in, the Sonic from the original games) & travelling through levels from past games in Sonic Generations.
• Harvest Moon celebrated its tenth anniversary with two games. One of the two games, Magical Melody, featured various characters from the original SNES game.

Web Original

• Linkara's anniversary episodes always have to do with Spider-Man's Clone Saga, because that's what his very first video review was about. He also celebrates the anniversaries of the show proper (the anniversary of his text recaps as opposed to video reviews in general) by reviewing an issue of Youngblood, his first text recap.
• Homestar Runner's 10th Anniversary saw the re-creation of the children's book the Flash-animated web series was based on (The Homestar Runner Enters the Strongest Man in the World Contest) as an episode of said series.

Web Comics

• The 10th anniversary Joyce & Walky! comic was a redrawn version of the first two Roomies! comics, keeping the dialogue in place until the surprise twist at the end.

Western Animation

• What was intended to be South Park's 100th episode (it was actually the 97th) starts out with the events of the first episode repeating exactly as before.