Thematic Series

You've heard a lot about this movie series dealing with the trials and tribulations of sushi chefs. The first film in the series revolved around a young sushi chef in Meiji-era Tokyo and how he hopes to open his own restaurant. You loved it so you get ready for the next installment... only to find that it is set in a modern New York sushi restaurant and features completely different characters. What gives? Sure, you know for a fact that it's a sequel, it has the same writer/director, and even several members of the Production Posse have returned, but it is essentially a different story that happens to be about a different sushi chef in a different time and place. You recognize the same concepts, the same ideas, and the same plot points but with different characters in different surroundings.

Unlike a typical series, a Thematic Series does not follow the same characters or story. Instead, it follows the same themes. One might recognize a few nods to past installments here and there. If the installments share any characters at all, they will be side characters or it may be in the form of a cameo by a former main character of a different chapter. This is assuming the installments take place in the same universe at all. Otherwise, expect Negative Continuity.

This is different from a Spiritual Successor in that the stories were all made by the same creators for the purpose of an interlocking series. Considering the nature of this series, audiences never have to worry about Archive Panic or Continuity Lock Out and can even see them out of order. Often, these series end up being trilogies.

Not to be confused with a Non-Linear Sequel, which is a videogame trope concerning a series that still follows a set group of characters and game elements, but plays fast and loose with the timeline or continuity.

Comic Books

 * Northlanders by Brian Wood. Each story arc takes place during the viking age but centuries apart and in locations as far apart as Iceland and Russia.
 * Sin City is about the eponymous city more than specific characters. While many stories share protagonists, they are all stand alone tales that deal with Noir elements.

Film

 * The Three Colors Trilogy by Krzysztof Kieslowski features three movies (Blue, White, and Red) about three different women in modern French society. Each color corresponds to different French revolutionary ideals. Different characters have brief cameos through the films.
 * The Three Cornetto Flavours Trilogy by Edgar Wright, Simon Pegg and Nick Frost is named after Kieslowski's trilogy. So far, it consists of a rom-com-zom (red), a buddy cop film (blue), and a third film titled The World's End (green).
 * Park Chan Wook's Revenge Trilogy: Sympathy for Mr. Vengeance, Old Boy, and Sympathy for Lady Vengeance. All three movies deal with revenge and its tragic consequences. While they have the same writer/director and many of the same actors, there is nothing to suggest that they even take place in the same continuity. In fact, Oldboy was based off a pre-existing Japanese manga.
 * The View Askewniverse movies (formerly The Jersey Trilogy) all take place in the same continuity, feature Jay and Silent Bob, and mostly take place in the same New Jersey town. Despite this, Clerks II is the only direct sequel (to Clerks). The movies all focus on different characters and plots, even crossing over into slightly different genres. Mallrats was more of a teenage Sex Comedy in the tradition of John Hughes,Chasing Amy was much more of a dramedy than any other installment in the series, and Dogma went into the realm of supernatural fantasy.
 * Greg Araki made a series of movies dealing with teenagers in or around the Apocalypse called, appropriately enough, The Teen Apocalypse Trilogy. The Doom Generation is the most well-known but it also contains the films Nowhere and Totally F---ed Up. None of them share the same characters at all (although they have a few of the same actors) and due to the apocalyptic nature of the films, it's safe to say they don't even take place in the same universe.
 * The Halloween series was meant to be such after the second film. Originally, every sequel would tell a different horror story set during Halloween. This is the reason why Halloween III does not include Myers. This idea proved unpopular with fans so the series ended up being all about Myers.
 * The Dollars Trilogy consists of A Fistful of Dollars, For a Few Dollars More and The Good the Bad And The Ugly. Clint Eastwood is in all of them, playing The Man With No Name but there is no story connection. It's made all the more confusing by the fact that Eastwood's character goes by a different nickname in each film.
 * To confuse things further, The Good the Bad And The Ugly, the third and final part of the trilogy, has The Man With No Name acquiring the hat and poncho he wore in the first film, A Fistful of Dollars, leading to the theory that all three movies are about the same character, but with different aliases. (it helps that each film takes place earlier than the previous one - TGTBTU is in the American Civil War, Lee Van Cleef's character in For a Few Dollars More appears to be a Confederate veteran, and A Fistful of Dollars has fully automatic machine guns and a gravestone dated 1873)
 * A more typical example of this would be with Leone's second trilogy, beginning with Once Upon a Time In The West, continuing into Duck You Sucker, and finally ending with Once Upon a Time In America. All of them take place in different time periods, beginning with the Wild West (somewhere around the 1880's), the Mexican Revolution (just before World War I) and finally over the course of the early twentieth century. According to Leone, the connection was that these were all time major events which touched America.
 * Not intended as a series, but Terry Gilliam refers to Time Bandits, Brazil, and The Adventures of Baron Munchausen as his "Imagination Trilogy".
 * In a similar manner, John Carpenter has what he considers his "Apocalypse Trilogy" starting with The Thing, going into Prince of Darkness and ending with In the Mouth of Madness. As the name implies, the connection has to do with each of the films presenting a scenario that could potentially result in the end of the world, by way of alien invasion, the rise of Satan, and blurring the lines between fantasy and reality, respectively.
 * The George Romero zombie movies (and most zombie movie franchises) never keep the same characters or setting but are all still a part of the same series. Part of the reason for this is because of the Kill'Em All plots.
 * Home Alone 1 and 2 have the same cast and thus do not follow this trope, however, Home Alone 3 has a new cast, keeping only the general plot of a home alone child confronting robbers the same. The movie also retains its setting in Chicago; there is even at one point a brief glimpse of Kevins house from the first two films.
 * Baz Luhrmann refers to his first three films -- Strictly Ballroom, William Shakespeares Romeo and Juliet, and Moulin Rouge -- as "The Red Curtain Trilogy". They are connected by common themes and cinematic style, not by any plot or characters.
 * The National Lampoon movies are essentially connected by the NL label and its writers. The only exception being National Lampoon's Vacation movies, which forms a more standard series.
 * Nicolas Cage had an action trilogy of The Rock, Con Air and Face Off, also known as "beige Volvo trilogy" due to said car being referred to or appearing in each.

Literature

 * The Dr. Seuss books are often considered a series. Certainly, they all share the same tone, writer, and artist. The characters and setting typically have the same design styles; the rhyming scheme is always present, as are the aesops.
 * Much like their films, the National Lampoon series of books don't form an interconnected series but rather, share the same writers.
 * William Hope Hodgson actually stated that three of his horror/fantasy novels - The Boats of the "Glen Carrig", The House On the Borderland, and The Ghost Pirates formed "what, perhaps, may be termed a trilogy" despite them not having the same settings or characters (and possibly not even the same continuity). Rather, they seem to all revolve around ideas, namely how little mankind really knows about the Earth - and even reality - and the mysteries and dangers that lurk just beyond our perception, sometimes in the midst of places and things that we take for granted.

Live Action TV

 * Super Sentai (less so for Power Rangers).
 * Kamen Rider as well: the main character will have large bug-esque eyes in suit-form, they will kick things, and they will ride a motorbike. Apart from that, everything changes from season to season, with the exception of Black and Black RX.
 * The Charlie Brooker series Black Mirror consists of three short films: the first one is set Next Sunday AD and involves the Prime Minister being forced into bestiality on live TV, the second is set in a distant Cyberpunk dystopian future where the masses are sedated by reality TV and Casual Video Games, and the last is set in a near-future world where people's memories can be stored like TV shows on a Tivo/Sky Plus box. The connection? All three are about the dehumanising influence of technology, with a particular focus on the pros and cons of total connectivity.
 * Tales of the Unexpected is a series of unrelated short stories revolving around blackly surreal horror behind everyday lives.

Video Games

 * The Final Fantasy series has few actual sequels. Most games take place in alternate realities, although there is some small overlap. All the worlds do exist in the same multiverse, though, since Word of God confirms that Gilgamesh is the same person in (almost) every appearance.
 * Enix's Heaven/Earth series: Actraiser, Soul Blazer, Illusion of Gaia, and Terranigma all revolve around restoring a destroyed Earth and defeating the great evil that was responsible for destroying the Earth, with the main character disappearing after his job is done. They were all at least published by Enix.
 * The Team Ico Series consists of Ico, Shadow of the Colossus, and The Last Guardian which are standalone games that take place in the same universe, share visuals and gameplay, and are all connected by the appearance of horns on certain characters, which mark them as sharing the blood of a god.
 * The Seiken Densetsu Series by Square, include a mythical sword that from all other famous Swords are based from(as in they are all the same Sword, just different name on different eras), also, the world commonly has it's own Tree of Life, and there are various espers guarding the elemental forces of the world(probably orbs).
 * The Shining Series has barely has any links between the games, with only the odd characters or locations turn up again. He even switches over genres a few times too.