Merida and Astrid never meet due to Astrid being a DreamWorks character, while Merida is a Disney/Pixar character.
Both Astrid and Merida are tomboys in their own unique ways, as they are both skilled in combat and their signer weapon, an axe and bow, and a few other weapons when needed like the warriors they surround themselves with, which helps them to take on ferial beasts, and enjoy showing off their skills. Since Merida displayed the full might of her archery skills in the contest for her hand, while Astrid wanted everyone to see her as the winner of the dragon (killing) training. They also have short fusses when their anger gets the better of them which sometimes gets them or their allies into trouble, Merida is the big sister of her little triplet brothers who are viewed as wee devils, while Astrid is friends with a pair of twins who leave chaos in their way when it comes to their pranks or need to explode something. Even though Merida is the daughter of DunBroch's King and Queen while Astrid is a valuable ally to Berk's chief and his family, before she becomes a part of the Haddock family as New Berk's Chieftess. Similar to how Merida's OUAT counterpart in the Once Upon A Time was crowned the new Queen of DunBroch, after she was able to turn the three Clan Lords from enemies to friends, along before Merida's coronation however her father, King Fergus, was killed in battle. Just as a few of Astrid's allies, like Heather, Dagur and Eret, were once her enemies, while Stoick was killed in their first battle with Drago at Valka's mountain.
Even though Merida rides a horse, Angus, on the ground while Astrid sores in the air with her dragon, Stormfly, the two both enjoy feeling the wind in their hair as they ride Angus and Stormfly at top speed through the woods, and have them around as they keeping their fighting related skills sharp. Before Astrid befriended Stormfly, dragons were the enemy of her people, while Merida's people hunted down bears because of Mor'du and it became a problem when her mother was turned into a bear. Just like how Astrid takes care and protects Stormfly and other dragons she comes across, Merida had to both protect and help Bear Elinor within and outside the caste and forest. There have even been times where Stormfly helps and protects Astrid, while Merida's little brothers in their bear cub forms had helped their sister save their mother. As for their main, animal, antagonists, Mor'du and the Red Death, both Merida and Astrid had a hand in their deaths.
Astrid's first signer color was light blue and Merida has worn a light blue colored dress, along with both of them having blue colored eyes, and just as Merida's signer weapon is a bow, Astrid had used one, in both the second HTTYD film and the Race to the Edge Netflix TV series, to shoot a flaming headed arrow in order to set a furaneol Viking ship a blasé. While Brave: The Video Game has Merida uncovering a magical charms that coats her arrows in fire, which has helped Merida on her journey in the game. The video game also has Merida traveling to icy and shoreline locations, and Astrid has been to similar landscape locations in both the HTTYD films and TV series. Along with both Merida and Astrid's homes, DunBroch and (old and New) Berk, being close to water and are surrounded by the green of the forests that sites next to their home settlements.
Meristrid is the main femslash ship of the How to Be Brave crossover fandom and a secondary/honorary femslash ship of the Rise of the Brave Tangled Dragons crossover, where Merida and Hiccup are part of the Big 4 along with Jack Frost from Rise of the Guardians and Rapunzel from Tangled, that sometimes has Astrid, along with Toothiana and Flynn, is one of its secondary or honorary members of the RotBTD crossover. Merida and Astrid are also largely/mediumly part of The Big Four Ladies, where Astrid and Toothiana take Hiccup and Jack's places in a female only group version of the Big 4 fandom, beside Merida and Rapunzel. It is less popular than Merunzel, even though in its own way the ship is a femslash version of Mericcup.
Despite there being fans who rival Meristid with both Mericcup and Hiccstrid, as Astrid and Merida fight each other for Hiccup's heart, there are a few fanfics and artwork that have the two as friends, allies and sister in arms, like Astrid is with Heather. As Merida helps Astrid to improve her archery skills, while Astrid teaches Merida how to ride a dragon. Even though Brave has mentioned a feud between Merida's kingdom and vikings. As such, it has lead to fanfics of Astrid's tribe being enemies of DunBroch, commonly in Mericcup as their leaders and families/friends work to create peace between their people and lands. The same analogy can be used in Meristid. Since in their own way Merida and Astrid aren't soo different from one another when it comes to their combat skills and looking into the face of danger in order to save the people they love.
In a few Brave/Celtic and How to Train Your Dragon/Viking AUs, fans have Merida as Astrid while the blond haired Viking Dragon Rider is seen as the DunBroch princess. Along with a few manip fanart featuring the two in each other's clothing for those AUs, for fun.
On AO3, the ship has 14 fanfics in total, while fanfiction.net has 54 with only 1 placed under pairing. The ship also has a reasonable size fanbase on both Tumblr and Deviantart.
|SHIPS||het||Astret • Dagala • Heatcup • Heathlegs • Hiccanna • Hiccelsa • Hicclena • Hiccpunzel • Hiccstrid • Mericcup • Moaccup • NightLight • Stalka|
|femslash||Astriana • Astrunzel • Heastrid • Heathelsa • Meristrid • Valkinor • Valkstrid|
|slash||Eretcup • Hijack • Variccup|
|family||Dagther • Stoccup • Valccup|
|CHARACTERS||male||Hiccup Horrendous Haddock III|
|female||Astrid Hofferson • Heather|