The 21st entry into the Marvel Cinematic Universe was Captain Marvel and it was the audience's first time seeing Carol Danvers aka Captain Marvel. The standalone filmed directed by Anna Boden and Ryan Fleck not only introduced fans to a new member of the Avengers, but also to the Skrulls.

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The Skrulls are a prolific alien race of shapeshifters featured in various Marvel comics such as Fantastic Four, X-Men, and Avengers. There is so much more to them than the little shown in Captain Marvel. Here is a list of 10 fun facts that weren't covered in the movie.

The Origin Of The Skrull

The Celestials are a god-like race introduced into the Marvel comic universe. These Celestials visited planet Skrullos and experimented on the existing race that resided there, which resulted in the creation of the three types of Skrull species - the Prime, the Deviants, and the Eternals. The Prime are the original species that became extinct after a bloody war with the Deviants. The Deviant Skrulls are the most familiar to fans of Captain Marvel, with their pointed ears, green skin, and their abilities to shapeshift into people and filing cabinets.

Specifics Of Skrull Biology

The Skrulls are a humanoid species and have both reptilian and mammalian traits. Physically, the differences between male and female Skrulls are similar to the differences in humans as far as stature and biology are concerned. Skrull women have mammary glands that they use to nurse their young, but as far as reproduction goes, the Skrulls lay eggs rather than giving birth. Their abilities allow them to shift into almost any being or object, but the movie didn't cover the their ability to shapeshift weapons onto their bodies or stretch like Mr. Fantastic.

The Reason For The Kree/Skrull War

The war between the Kree and the Skrull is heavily referenced in the movie as an ongoing conflict, but the origins are never explained. The short version is that the Kree/Skrull war began with a contest. The planet of Hala was once inhabited by two groups - the Kree and the Cotati.

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The Skrull Empire arrived on Hala and instigated a competition to decide which group would represent the Empire. Once the Kree realized that the Cotati were going to win, they destroyed them all. The Skrulls were extremely upset by this, but the Kree turned on them as well and murdered the Skrull delegates, then stole their technology. This began the decades-long war.

Their Gender and Sexual Fluidity

One of the most unique details about the Skrulls' ability to shapeshift is that they replicate the host down to the DNA level. This is mentioned in the movie, but the deeper implications are only explored in the comics. The Skrulls are reproductively compatible with many species and their gender fluctuates due to their shapeshifting. This means that a Skrull male can sim a human woman, then get pregnant and bear a child, all while still technically being a biologically male Skrull. This promotes gender and sexual fluidity among the Skrulls.

Talos Can't Shapeshift (In The Comics)

Expertly played by Ben Mendelsohn, the General Talos in Captain Marvel brags about his superior shapeshifting abilities that take "practice, and dare I say, talent." The character that goes by "Talos the Untamed" in the comics is a little bit different.

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One of the biggest changes is that in the comics, Talos can't shapeshift. This is a rare genetic defect among the Skrull. While Talos lacks the power of shapeshifting, he does have above-average strength and endurance, which is a common side effect for Skrulls with this mutation.

Some fans have pointed out the visual similarities between the appearance of the Skrull in Captain Marvel and Thanos in the various Avengers films. The two aren't exactly the same. Thanos doesn't share the shapeshifting powers of the Deviant Skrull and his skin is purple, while Skrulls are green. Still, their faces do bear a resemblance, specifically with their deep, lined chins. This is because Thanos is a part of companion race to the Skrulls created by the Celestials  - The Eternals - and he carries a Deviant Skrull gene from his mother.

Skrull Assimilation Wasn't Just On Hala

The Skrulls are portrayed in the MCU as a race of refugees that have been driven from their homes by the Kree and forced to shift to fit in on Hala. This isn't entirely untrue, but it is different from the conquering race of villains that fans have seen in the past. In the comic book universe, the Skrulls tend to be more dominant. They often assimilate to other planets and cultures rather than living in their own skin. They have done this both peacefully for their protection and in an effort to infiltrate and dominate whichever planet they were visiting.

The Skrull Have A Rich Culture

The Skrulls are a warrior race, but Marvel has crafted a detailed history for them to include a rich culture. They hold a code of honor that forbids them from harming anyone who has saved their life and also they also have respect for the concept of a fair fight.

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There is not only a Skrull language, but it has many dialects including Skrullian, Tligi, and Frti. The Skrulls also have a religion known as D'ardvan, or the "True Faith," and they even have their own belief in a version of Hell. The Skrulls are known to go on vacations to the Kral System, which mimics periods of Earth history.

They Have Appeared In Many Comics and TV Series

The Skrulls' primary role as the villains was subverted in Captain Marvel, but they have been a consistent part of the Marvel universe since 1962 when they appeared in Fantastic Four #2. The alien race appeared often in the Fantastic Four series, and Johnny Storm AKA The Human Torch even has a relationship with a Skrull woman named Lyja, but that isn't where their story stopped. They have also been featured in various Marvel video games, comics such as Avengers and The Incredible Hulk, and in the 1990's cartoon television series X-Men.

There Are Super Skrulls

A Super Skrull named KI'rt first appeared in Fantastic Four #18 in 1963 as an antagonist to the Fantastic Four, and more have followed through the years. The original Super Skrull, KI'rt, is a formidable foe. He not only has shapeshifting abilities but is a skilled fighter and pilot. He also has powers that mimic those of the Fantastic Four including super strength, super stretch, flight, durability, and invisibility. He brings one new power to the table too with hypnotic powers that can freeze people around him just by looking them in the eyes.

NEXT: 10 Best Talos Quotes In Captain Marvel