Always Identical Twins

Think of your favourite pair of fictional twins. Got them? Now, be honest: Are they identical twins?

If you answered "yes," there's a reason for that. Identical twins show up far more frequently in fiction than fraternal (non-identical) twins. If you don't believe us, take a Wiki Walk through Twin Tropes. We'll wait.

So why are fictional twins always identical? Well, for starters, identical twins are visually striking. They allow for comic plots, and they add symmetry and symbolism to a story. An Evil Twin is almost always an Identical Twin; how else could they impersonate the "good" twin? Fraternal twins, for all intents and purposes, are just regular siblings, and regular doesn't cut it in fictionland.

This trope is so pervasive that it even manifests when the twins are different genders-- Half-Identical Twins shouldn't even be identical!

There are sometimes aversions, almost exclusively in live action productions where twin actors or Double Vision are not available. The main subversion of this trope is Non-Identical Twins, when twins are said to be identical but are obviously not.

Identical twins are highly prone to Speaking In Unison or Finishing Each Other's Sentences.

In reality, fraternal twins are significantly more common than identical twins—only 8% of twin births are identical.

Examples of Always Identical Twins include:

Identical Twins

Anime & Manga

Fujio Akatsuka's Osomatsu Kun is about identical sextuplets. Yes, SIX characters that look exactly alike. The running gag in the early episodes was that other characters couldn't tell which is which.
Ouran High School Host Club has the Hitachiin twins, who are so alike that no one had ever been able to tell them apart until they met Haruhi. Of course they use that similarity for their own amusement.
Tsubasa Reservoir Chronicle has Fai and Yuui , the "twins of misfortune" who are practically the same child made twice.
- Horitsuba Gakuen has the above mentioned twins as well as Syaoran and Syaoron.
It is fairly common in most harem-type series to have a pair of identical twins as part of the cast.
Played with in Eyeshield 21. Agon and Unsui dress and act very different from each other and whether they were fraternal or identical was left somewhat ambiguous for most of the series. However after Agon gets a haircut, everyone is amazed to see he and his brother are very much identical.
Mion and Shion Sonozaki from Higurashi no Naku Koro ni use this to their advantage, as they often assume each other's identity to manipulate and cover up murder. The roles between psychopath and victim switch depending on the arc.
Naruto features two sets of identical twins (Hiashi and Hizashi and Sakon and Ukon). Coupled with Shadow-Clones and Generation Xerox, Masashi Kishimoto seems fond of twins; he himself is one.
Yoh, the protagonist of Shaman King, is revealed to be the identical twin of Hao, the Big Bad of the series.
Played with in Maomarimo: Mao and Ako remain fraternal twins even after Mao's Gender Bender, but the issue is raised by a background character who wonders why this trope wasn't invoked.

Comic Books

Wendy and Goldie, twin prostitutes from Frank Miller's Sin City. According to Marv, they even smell identical.
Mandrake the Magician and his Evil Twin Derek.
The Trigger Twins, from DC Comics All-Star Western series.
Lightning Lad and Lightning/Light Lass of the Legion of Super-Heroes, who are fraternal twins, come from a planet where nearly everyone is born with a twin sibling. The reason their older brother Lightning Lord is evil is because he was born without a twin.
Huey, Dewey, and Louie from the Disney Ducks Comic Universe, with bonus rhyming names. They have Color-Coded for Your Convenience hats: red is Huey, blue is Dewey, and Louie is green or yellow, depending on the colorist. Yellow was more prevalent in the 4-color era, but by the time of DuckTales (1987) green became the standard, possibly because of RGB screens.

Fanfiction

Ethan and Evan Brightman from the Glee fanfic Dalton, who are heavily based on Fred and George Weasley.

Film

There are identical twin brother cops in Hot Fuzz -- the Sergeants Turner (Bill Bailey's characters).
Mary Kate and Ashley Olsen in everything they've done (except Full House, where the twins both played the same one character to stretch limits on how long very young child actors are allowed to work). They're actually fraternal twins, but look alike enough for identical-twin plots to work.
Both versions of The Parent Trap.
The Prestige: Borden and Fallon.
The Stabbington Brothers in Tangled.
A pair of elderly women twins appear in the French film Amelie, buying food at the local fruit stand. They also finish each other's sentences.

Literature

Harry Potter: Fred and George Weasley and the Patil sisters
The main character and his brother from The Spiderwick Chronicles
The main characters of the T*Witches series.
Jessica and Elizabeth Wakefield of Sweet Valley High.
- Not to mention the identical evil twins Nora and Margo, who other than hair color are so like Elizabeth and Jessica that they're even able to fool the twins' parents.
Subverted in Honor Harrington: while Detweiler brothers look like identical sextuplets, they are, in fact, clones of their father.
Elladan and Elrohir of The Lord of the Rings are not outwardly stated as being twins or even identical, but because their birth year is the same and elves wait at ten years between children, they are assumed to be twins. They are also said to be "So much alike were they, the sons of Elrond, that few could tell them apart: dark-haired, grey-eyed, and their faces elven-fair, clad alike in bright mail beneath cloaks of silver-grey." This implies that they are identical twins.
Lampshaded in Chronicles of the Kencyrath, where the Edirr produce so many twins they usually do everything in twos.
"The twins" (No Names Given) in Peter Pan, "who cannot be described because we should be sure to be describing the wrong one." Note that Peter doesn't really know what "twins" are, and the animated series Peter Pan and The Pirates brutally subverted this trope by making the twins different colors and heights, the implication being that they're merely good buddies who were labelled "twins" because they are always together and finish each other's sentences.
Jory and Nia from Cold Fire.

Live Action TV

Tia Landry and Tamera Campbell on Sister, Sister are long-lost identical twins, played by real life twins Tia and Tamera Mowry.
Zack and Cody on The Suite Life of Zack and Cody, also played by Real Life twins. Puberty made them not so identical.
Nearly every set of twins in The Pretender, from regular character Sydney and his brother Jacob down to the briefest one-off appearance. Particularly notable was the episode where Sydney visits a Twins Convention, which is populated entirely by identical twins sticking together and wearing co-ordinated outfits.
The Bold And The Beautiful had a rather interesting example. Twins Stephanie and Phoebe Forrester were identical twins until they graduated high school. From that point on they've been fraternal.

Tabletop Games

The Ravenloft setting has Laurie and Gennifer Weathermay-Foxgrove, identical twin monster-hunting heiresses, as well as Jacqueline and Louise Renier, identical wererat littermates.

Theatre

The mix-up in The Comedy of Errors is caused by two sets of identical twins confusing themselves for each other.

Video Games

Dante and Vergil from Devil May Cry, of the symbolism-heavy, Cain and Abel, Polar Opposite Twins variety. You can tell them apart because Vergil slicks his hair back, but they're also Color Coded for Your Convenience: Vergil wears blue, Dante red.
Redmond and Blutarch from Team Fortress 2, you can only tell them apart because Redmond wears a red suit and Blutarch wears a blue suit
Ami and Mami Futami of The Idolmaster.

Web Comics

The Order of the Stick: Elan and Na le.

Web Original

Melanie and Militia Malachite from RWBY, twin Elegant Gothic Lolita bouncers at a Bad Guy Bar.

Western Animation

Patty and Selma and Sherri and Terri from The Simpsons
Dee Dee and Di Di from Batman Beyond
Lo and Li, Azula's ancient caretakers, from Avatar: The Last Airbender. ATLA also had a set of twins in the episode "The Fortuneteller," who were identical except one was an Earthbender and one wasn't.
Kim Possible's little brothers are identical twins who can only be told apart by the colour of their shirts.
The Scottish Twins from Thomas the Tank Engine zigzag with this trope. In their backstory the twins intentionally removed their number plates so as to appear completely identical and pull a Twin Switch and escape from a railroad that threatened to have them scrapped. After being employed at Sodor, though, they were given number and name plates, specifically so they could be told apart.
Ingrid and Latoyah from Slacker Cats.
Más y Menos from Teen Titans.

Real Life

The village of Kodhini, India has 6 times as many twins as the global average. On top of that, the majority of the twins are identical.

Fraternal Twins

NOTE: This section is reserved for sets of twins—same sex or different sexes—who do not look alike; brother-sister twins who do look alike go to Half-Identical Twins.

Anime

Kirio and Kirika from Kamichama Karin.
In Corsair, fraternal twins Aura and Leti are clearly related yet distinct, with Leti taking much more after their father's side and Aura taking more after their mother's side.
"Syaoran Li" and "Watanuki Kimihiro" aka "Tsubasa Li 1" and, presumably, "Tsubasa Li 2 of Tsubasa Reservoir Chronicle and ×××HOLiC are a particularly notable example, being that they're not identical despite one of them being a time travel duplicate of the other.
Gundam SEED's Kira and Cagalli, being largely based on Luke and Leia. In addition to being non-identical, one is a genetically engineered superman and the other is completely unaltered.
Kagami and Tsukasa Hiiragi from Lucky Star are fraternal twins who are drawn to have very different eye shapes (Tsukasa has Tareme Eyes and Kagami has Tsurime Eyes) and they also have different hairstyles. However, they do look more similar to each other than to any of their other family members, at least as far as their hair and eye colors are concerned.
Karin and Yuzu Kurosaki of Bleach.
Mairu and Kururi Orihara from Durarara!!, though they are sufficiently similar to possibly be just identical twins who decided to look different.
Rin and Yukio Okamura from Ao No Exorcist are fraternal twins who - despite looking somewhat alike when you take away Yukio's glasses - are opposites in pretty much everything, up and including Rin being (half-)demon and Yukio being human. This didn't stop the fandom from going nuts with Twincest.
Princess Fine and Princess Rein of Fushigiboshi no Futagohime (Twin Princesses of the Mysterious Star).
Kyou and Ryou Fujibayashi of Clannad are similar to Kagami and Tsukasa Hiiragi in that Ryou has Tareme Eyes and Kyou has Tsurime Eyes. Though they're more alike than most fraternal twins with similar colored hair and eyes in the OVA for Kyou's route it takes Tomoya several minutes to realize that he's talking to Kyou and not Ryou after she cut her hair.

Comics

Ember and Suntop from Elf Quest.
The Phantom's son and daughter are twins.
Crystar and Moltar from Crystar Crystal Warrior.
Northstar and Aurora from Alpha Flight.
Charles Xavier and Cassandra Nova, although she apparently is not exactly human.
Quicksilver and Scarlet Witch: different genders, different hair colors, and different power sets.