The first anime film was meant to tie up loose ends and make sense of certain events in the first season. Later films in the series were more standalone, though still considered in continuity. Interestingly though, the tenth, eleventh, and twelfth movie feature an overarching storyline involving the three Dragon legendaries of Sinnoh.
It is worthy to note that the first movie was once intended as a Grand Finale in the early production process, indicated by early teasers, but that plot was dropped later because of popularity.
There are now twenty-three of them, two of which are actually one for the price of two.
Macross: Do You Remember Love? told an alternative version of the events of the Super Dimension Fortress Macross series, and was later retconned into appearing in later Macross series as a fictional movie produced in the Macross-verse twenty years later, telling a garbled version of events that the few survivors had witnessed.
Macross Frontier got two: The False Songstress and The Wings of Goodbye, which are like its versions of Do You Remember Love? In short, like DYRL?, they're an alternative version of the events during the Frontier anime series, but split in two movies, with the last one actually resolving the love triangle.
Adolescence of Utena takes the series' already-difficult-to-understand (at least for Westerners) Buddhist allegory, compresses it into two hours, and makes it even more allegorical. The resulting head trip of a film requires advanced knowledge of Jungian theory, and knowledge of Gnostic belief to understand at all. (Although, viewing the series first, and learning about its symbolism does make the movie much more understandable, particularly the cars.)
The Vision of Escaflowne movie radically altered characters and motivations, hitting similar themes in a very different way than the series.
The RahXephon movie made similar radical alterations in the attempt to compress a season's worth of difficult-to-understand story into two hours.
Bleach has four movies. The first is about a group of rebels trying to destroy Soul Society, the second is about Captain Hitsugaya trying to clear his name, the third is about people forgetting Rukia and Ichigo, and the fourth is about Hell.
Robotech was set to have a movie which used footage from Mega Zone 23, but a combination of Executive Meddling and poor reception in test screenings caused it to be shelved.
The '90sSailor Moon anime had three, one in the second season (Sailor Moon R The Movie), one in the third (Sailor Moon S The Movie), and a final in the fourth (Sailor Moon SuperS The Movie). None have anything to do with their corresponding seasons but seem to take place in just 'somewhere' in them. The S movie is the only one directly based on anything, a standalone manga chapter, The Lover of Princess Kaguya, Naoko Takeuchi wrote purposefully for adaption... there are quite a few plot diversions between them though. Oddly enough, the 1st and Sailor Stars seasons never got movies for them...
The SuperS movie is notable for having a traditional episode style title. Its full title is Sailor Moon SuperS: The Movie: The 9 Sailor Senshi get together! Miracle in the Black Dream Hole! The other two don't have any titles aside from Sailor Moon R/S: The Movie. (Though the English dub tacked some on anyway - Promise of the Rose, Hearts In Ice and Black Dream Hole.)
Two movies also premiered with a short special. R had Make-up! Sailor Senshi, which introduced the Sailor Senshi and SuperS had Ami-chan's First Love (based off the manga chapter of the same name). During the run of the SuperS season, a 45-minute special episode was aired containing 3 shorts: An Elegant Metamorphosis? Crybaby Usagi's Growth Diary a recap of the first 3 seasons, Haruka and Michiru, Again! The Ghostly Puppet Show, which shows what Uranus and Neptune are doing during SuperS, and Chibiusa's Adventure! The Dreaded Vampire Castle which has the Sailor Senshi fight a vampire and is loosely based on a manga side-story.
Fist of the North Star has the original 1986 movie, which was basically a Bloodier and Gorier big-budget version of the earlier TV series produced by Toei (who also did the TV series); the Legends of the True Savior movies from the late 2000's, which also retold events from the manga, but with new story elements; and the Live-Action Adaptationfrom 1995.
It does fit in passably, considering the episodic nature of Cowboy Bebop - a reasonably long amount of time could pass between any two given episodes.
Given that Big Shots is still on, but we see a cameo of Andy as a ronin instead of a cowboy (which happened at the end of the episode he was in) it'd easily take place between episodes 22 and 23.
Ghost in the Shell: Solid State Society is effectively the show's "Third Gig", although it only occupies one film rather than a whole series. It shows. (Not in a directly bad way, it's just glaringly apparent.) There are also two movies, "The Laughing Man" and "The Individual Eleven", which are basically compilations from the two original season arc episodes. These two films have been criticised for compressing the plots so much that they are hard to follow, and also for the fact that the English dubs were not performed by the actors who dubbed the series.
The movie was actually intended to be the first part of a trilogy, with two Japan-only video games filling in the blanks between the series and movies.
Another movie was later released retelling the second season and is notable for Adapting Out Gil Graham and his familiars.
A two-part third movie was also made, but rather than adapting the third season it takes place during the Time Skip with elements from the PSP games (it would be impossible to adapt StrikerSIn-Universe without drastically altering the story due to the amount of classified information involved).
Pretty Cure has roughly one movie of this sort per series. (If Hikari hadn't been in the first movie, it would have been exactly one per series.) Like the Sailor Moon movies mentioned above, all of them are disconnected from the parent series' plots but seem to take place somewhere along the way.
You also have the All-Stars movies, focusing on the teams meeting up and fighting an original villain. More recently, due to the overwhelming amount of Cures, the movies tend to focus on the three most recent teams.
Tengen Toppa Gurren Lagann had two movies: Gurren Chapter and Lagann Chapter that were essentially summaries of the original series with new animation put in. Don't let that fool you though. In Gurren-hen the beginning of the movie shows Lord Genome's rise to Spiral Knight and fall to despotic tyrant. Then it's pretty much the same until: Adine, Guame, Cytomander, and the new general: Viral (Yes that Viral, complete with his own Enkidu-daiganzan) all attack the Dai Gurren-dan at once. Simon later snaps out of his wangst after trying to climb Suzaku to save Nia. (Suzaku is at least a mile in the air at this point) The generals then combine their mechs to form the Dai-Gan Doten-Kaizan which falls after a combined attack by the entire Dai Gurren-dan (GIGA DRILL BREAKER! DAI GURREN-DAN SHOOT) Lagann-hen then takes the last episode of the series and raises it to the power of itself after: The ENTIRE Dai Gurren-dan (Only Kittan died, the rest of the Mauve Shirts survived) get their own Tengen Toppa Ganmen. (Even Nia) After Lord Genome converts the Big Band Storm all of the ganmen combine to form SUPER Tengen Toppa Gurren Lagann. From Super Tengen Toppa Gurren-Lagann's drill comes Tengen Toppa's drill. From Tengen Toppa's drill comes Chouginga Gurren-Lagann's drill. From Chouginga's drill comes Arc Gurren-Lagann's drill. And from Arc's drill comes Gurren-Lagann. Viral does a Cannonball Attack. Then Lagann does a Cannonball attack. And then Simon and the Anti-Spiral fistfight. Then Simon turns his own blood into a drill and goes straight through the Anti-Spiral.
Slayers has five Non Serial Movies, but only the first is considered The Movie. Drawn to the mysterious resort island of Mipross by dreams planted in her head by the ancient wizard Rowdy Gabriev, Lina and Naga get involved in a battle against a demon named Joyrock that culminates in Lina being sent back in time to kill him before he could slaughter the elves of Mipross, an act that is stated to be directly responsible for the existence of Lina's companion Gourry Gabriev.
Sword Art Online the Movie: Ordinal Scale is set between the events of Mother's Rosario and Alicization. Augmented Reality technology kicks off, resulting in the creation of a highly advanced AU game called Ordinal Scale. Things begin to go horrifically awry, however, when monsters from SAO find their way into the game.
The movie version of X1999 was produced when the manga was still beginning. Because of this, many plot elements were over-simplified or cut-out completely, with one of the antagonists (Kakyo Kuzuki, who was yet to be introduced in the manga when the movie was made) being replaced with a new character (Shogo Asagi). The movie sets aside the conflict between the individual Heavenly Dragons and Earth Dragons to focus more on the relationship between the childhood trio of Kamui, Fuma, and Kotori.
The Disappearance of Haruhi Suzumiya, based on the light novel of the same name, was released 2010. At 162 minutes, it's the third-longest animated film ever, behind Final Yamato and the extended cut of In This Corner of the World.
Gintama has a movie adaptation of the fan-favorite Benizakura Arc. Also, in 2013, another movie with an original plot was released, supposedly to act as a 'final episode' for the Gintama anime. Though, considering how many times the staff has trolled the fanbase by claiming the show has been cancelled, there is a certain lack of credibility to this...
Eureka Seven has an Alternate Continuity movie which re-writes everyone's back story and motivations. It is connected to the series though.
The film series based on Doraemon has released almost 40 movies as of 2020, but since the story doesn't have a real ending nor does it have any development, plus most of what the studio's doing nowadays is to remake em' all for new generations of kids, all Doraemon movies (except some short movies and spinoffs) are considered non-serial movies.
It got a movie based on one of the routes in the game: Unlimited Blade Works. Like all anime adaptation movies, some things were cut, some scenes were changed, and some others possibly enhanced.
Dragon Ball has had many movies and movie-like features over the years:
The original Dragon Ball had three movies (and a special if one counts The Path to Power). They compress several arcs together whilst also doing their own thing.
Dragon Ball Z got 13 movies and two OVAs. While the OVAs are considered canon, almost all of the movies can't fit into the anime and often reuse themes and plotlines the anime was currently adapting anyway. Notably, thanks to the change in anime title they got to do "The Movie" again where the first movie was released as just Dragon Ball Z. In the mid 2010s there were two more films released, Battle of Gods and Resurrection 'F', which are the only Z movies that are canon to the anime series.
Dragon Ball GT got the Goku Jr. TV special. Unlike the classic movies, it was considered canon to the anime thanks to connecting with GT... but GT's canon status has been in critical condition ever since Super came out. It also had The Path to Power special during this era, but since it's a retelling of the story's beginning, it's officially recognised as the fourth Dragon Ball movie.
Officially Dragon Ball Super has only one film thus far, Broly, which is considered canon to the anime series (and effectively replaced the Bardock special). Notably however, Super's first two arcs adapted the two canon Z movies, Battle of Gods and Resurrection 'F', expanding and tweaking those stories, meaning those films could technically be considered canon in some fashion.
Steins;Gate has Steins;Gate: Burdened Domain of Déjà vu. It takes place a year later, and deals with a much different threat. This time, it's Rintarō Okabe's Reading Steiner ability. His memories of the other world lines are overloading it, causing him to shift out of the Steins;Gate world line. As a result, it's as though he never existed, and no one remembers him, except for Kurisu Makise and Suzuha Amane.
Tenchi Muyo! had two movies that were set in the Tenchi Universe continuity: 1995's Tenchi Muyo! in Love and 1999's Tenchi Forever! A third movie, 1997's Tenchi Muyo! Daughter of Darkness, was set in its own universe, derived from the OAVs.
Uiharu: The titular Endymion is the world's first space elevator! It has been under construction since 3 years ago without the city revealing what its purpose is! It is a bridge connecting Earth to space! Saten: Oh... Hey, Uiharu. If it's been under construction for three years, then that ridiculously huge tower was already there when this manga began, right? Has it really been here all that time? Uiharu: What are you saying, of course it has. Did Mental Out mess with your memories? Saten: But it's never been drawn in the background before... Uiharu: It just so happened to be outside the panel. Saten: Don't you call this a retco— Uiharu: IT JUST SO HAPPENED! TO BE OUTSIDE!! THE PANEL!!! Saten: O-Okay.
Subverted with Sonic the Hedgehog: The Movie, which is actually two thirty-minute OVA episodes combined into an hour-long "movie". The plot, which covered Sonic's fight to save the planet of Freedom from Eggman's schemes, was meant to act as a pilot for an anime series, but such a series never materialized.
Panpaka Pants had a 60-minute film titled Panpaka Pants The Movie: Treasure of the Bananan Kingdom, where a vacation with his family ends in him being separated and stranded in the Bananan Kingdom, where he meets up with Wanpoko the Dog, Terry the Monkey and Orson the Crane and must work with them to retrieve the Kingdom's stolen bananas from the Alligator King.
Demon Slayer: Kimetsu no Yaiba has a movie that adapts the Mugen Train arc. The movie itself is known to break several box office records. Eventually, it became not only the highest grossing anime film (beating out the likes of Spirited Away), but also the highest grossing R-rated animated film, the highest grossing Japanese film and even became the highest grossing film of 2020 (no really, it's mainly because of Covid which prevented a lot of American films to be shown theatrically).
