The MLP - Teen Titans comparison was well received so I was inspired to try again.
(The Teen Titans MLP Comparison: [link]
Also the personalities of the the MLP mane six and the Satam primary characters were uncannily close!
Antoine D'Coolette / Fluttershy:
Both are by their natures shy and awkward and could be considered cowardly and pessimistic. They also prefer peacetime pleasures to adventures or danger and have a sense of refinement and class they like to preserve in all things. They are also not unskillful fighters when their backs are against the wall or their friends are being threatened.
Reactions on Meeting: Neither would likely ever approach each other because both are cripplingly sheepish. But Fluttershy is more then willing to greet friends when she's certain they're safe, and Antoine highly regards his decorum so he'd likely greet her in a formal fashion, perhaps kissing her hoof.
Sonic / Rainbow Dash:
Both are speedsters, daredevils, reckless and exuberant. Their extraordinary athleticism is their distinction and a credit to their allies. Sonic and Dash are also a shade arrogant about their abilities, but brave enough to face any situation or foe, treating both like a personal challenge and another opportunity to improve themselves.
Reactions on Meeting: This is a friendship practically made to order. Sonic and Dash speak roughly the same way, have similar interests, probably move equally quickly and have the same devotion to loyalty. They might get on each other's nerves because of their mutual interest in being the best, but more likely it would lead to intense but friendly competition.
Bunnie Rabbot / Applejack
Both are hard-workers, heavy lifters, and front line battle units if it comes to a knock-down, drag out fight. They are both stronger then their fellows but use that strength to the advantage of their comrades and community. They also both have southern accents and wear wide brimmed hats.
Reaction on Meeting: This is another pairing that makes one wonder if the writers drew from SATAM when redesigning MLP. Bunnie and Applejack are alike enough to be sisters and would probably treat each other as such, endlessly occupied with telling each other ranch stories or boasting of their lassoing exploits.
Rotor / Rarity:
This might seem an odd and out of place comparison, but the similarities are there. Both are industrious, skillful craftsmen who love their work and putting in hard effort to improving the lives of their fellows. They're also patient, polite, and live solitarily.
Reaction of Meeting: Although from two social classes (Rotor decidedly low class, Rarity aspiring for the upper crust) these two might still get along. Rotor is friendly enough and Rarity, unless irritated by her workload, is open and amiable. Rarity's craft of costuming and Rotor's knowledge of machinery and computers could lead to a unifying conversation about working and diligence itself.
Miles 'Tails' Prower / Pinkie Pie:
Both (speculation in Pinkie Pie's case) are the youngest of their group. Both are enthusiastic, slightly hyper, and endlessly curious. Both are also inventive, fiercely devoted to their fellows, and have issues with self esteem and lack of purpose if pushed to the side. Tails and Pinkie also really enjoy a good party.
Reaction on Meeting: This would be something to see. Pinkie's reaction to anything is unpredictable and Tails tends to flee anything he doesn't completely understand, but the two could be brought into friendship if one of them got the other involved in a play activity, that being the way they both resemble each other the most. Maybe Tails could coax her into a video game or she could convince him to help her set up a birthday party.
Sally Acorn / Twilight Sparkle
Both are high born but awkward in their new surroundings. Both are leaders by nature and circumstance, followed easily by their fellows because of their bearing and tact. The two are also compulsive information gatherers, prone to extreme emotions, and tend to become exasperated at the antics of their groups: ever playing the straight man. Both however also have a mischievous side.
Reaction on Meeting: Once the subject of how insane their friends were was raised this would form into a life long alliance after a simultaneous sigh and eye-roll from both Sal and Twi.
Because Sally is interested in collecting data and Twilight is just a straight up book worm a library would be good unifying ground for the two. Also in small part they have a mutual appreciation for magic.