Different in Every Episode

This doesn't even begin to cover the weird things that you will frequently see on the Middleton High sign.

A Running Gag of sorts.

If a Couch Gag is where something different shows up every time in the opening sequence, this is where something from the episode itself is always different. Not just the obvious story telling devices like characters, plot, and settings, (though it can play into them,) but rather more mundane things that are different just because they can be.

May often overlap with Unlimited Wardrobe if most characters in the series are usually subjected to Limited Wardrobe, and one is different just because they can be.

Examples of Different in Every Episode include:

Anime And Manga

• In Kore wa Zombie Desu ka?, Ayumu's fantasies of Eucliwood are voiced by a different Seiyuu (frequently well known, but less commonly heard from nowadays) each episode. There is even a scrolling text placed onscreen saying who the Seiyuu is this week.
• In So Long Mr. Despair, the writing on the blackboard in the classroom, and a lot of writing seen elsewhere, will change in every shot, mid-coversation.

Literature

• Ms. Frizzle from The Magic School Bus will change her dress in every episode to reflect the subject being covered in that episode.

Live Action Television

• On Friends the Magna Doodle on Chandler and Joey's apartment has a different picture each time.
• The picture on Murphy Brown's Dartboard of Hate.
• The funny message on Frank's trucker cap on Thirty Rock.
• The Prisoner has a subtle aural example: the section of the opening theme tune accompanying the scene where the future Number 6 confronts his boss is remixed to emphasize different instruments in each episode.
• The number on the whiteboard in Battlestar Galactica Reimagined is a more-serious-than-usual example. It counts the population of the fleet and ticks down over the course of the series.
• Police Squad! had a few:
  • Once an episode, Inspector Frank Drebin would visit Johnny the Shoeshine Guy for "the word on the street". After getting oddly detailed information from Johnny, Frank would leave and someone else would come, asking for (and receiving) advice specific to their line of work. This second person was different every episode—a heart surgeon, a theologian, Dick Clark, etc.
  • Any time Frank Drebin parked his car, he would hit another car or some garbage cans. With every episode, the number of garbage cans he hit at once would increase.
  • The opening credits of every episode would feature a different guest star. Who would invariably die before the credits ended.
  • The first episode parodied the practice of playing the end credits over a freeze frame, by leaving the cameras rolling while the actors just stand really still. Every subsequent episode introduces a different variation on this gag: the actors all freeze while a chimpanzee trashes up the office in the background; an arrested criminal notices that everyone else is frozen and tries to escape; the actors continue pouring a cup of coffee during the credits until the coffee mug overflows, etc.

Webcomics

• The specials at Coffee of Doom in Questionable Content change every in-comic day.

Web Original

• The Spoony Experiment: Spoony does most of his reviews just sitting in a green chair while you can see posters hanging on the walls in the room corner directly behind him. In pretty much every review he does, he changes those posters to reflect something relevant to the review itself, usually a movie poster or wallscroll of the movie or game he's reviewing. If it's anything Highlander related, it'll usually be a poster of that movie. Anything Japanese game related, expect to see wallscrolls of the game or of Cowboy Bebop: The Movie.
• Similarly, The Angry Video Game Nerd would often switch up his background posters hoping people would spot the references.

Western Animation

• The chief of The Secret Show changes his name every episode for security reasons.
• Kimiko from Xiaolin Showdown has an Unlimited Wardrobe where she's always wearing a different outfit (and often hairstyle) in each episode simply because she can. Everyone else in the show is subject to a Limited Wardrobe, with a few special occasions as the plot of the episode demands.
• In Squidbillies, Early Cuyler's hat says something different in every episode.
• The pizza restaurant has a different theme and the museum offers a sample of a different exotic food in each episode of The Weekenders.
• On Bob's Burgers, the Burger of the Day that is posted on the wall changes every episode. It will also change during episodes that take place over multiple days.
• The sign outside Charles Darwin Middle School in My Gym Partner's a Monkey.
• The sign outside Middleton High on Kim Possible.