Image imported from ponerpics 
Original Description:
 
Friendship Is Magic: The Next Generation begins thirty years after the birth of Princess Flurry Heart, and the story is… a bit darker and more complicated than My Little Pony: Friendship Is Magic before it. It delves into the backstory around Alicorns, where they came from, why Discord is the only Draconequus, and who is the prisoner in the deepest darkest cell of the cosmic oubliette that is Tartarus…  
(And admittedly, FIM:TNG does take some liberties with the events of MLP:FIM, mostly in regards to Equestria Girls and all episodes after and including The Cutie Re-Mark. That will become more apparent when it comes to the character bios for Sunset Shimmer, Flash Sentry, Starlight Glimmer, and others.)
 
This here is Mousse Masquerade, age 25, born as Mousse Pie and known as Moosie to his more extroverted friends (and Mommy Pinkie), older brother to Sparkler Surprise. He is the residential costumer of Ponyville, residing in a shop left next door to Sugarcube Corner, opposite his little sister Sparkler’s party shoppe. He has received rave reviews for the uncanny likenesses of the costumes he creates, especially when he himself is wearing them.
 
Naturally, Moosie’s special talent is in producing costumes. As a colt, he was enamored of Momsy Rarity’s seamstress business and took to his own take on it, creating a deluge of costumes in every shape and size, representing every species on Gaia. He has special costumes that he keeps for himself, to live up to the latter half of his name.  
Moosie’s cutie mark on its own
 
Mousse Masquerade has an uncanny ability to perfectly fill out whatever full-body costume he wears, and he has one for seemingly every pony or person he’s ever met, no matter the size or number of limbs. And somehow, he is able to emulate those people perfectly whenever he wears the full costume. In Pegasus costumes, he can affect the weather. Disguised as an Earth Pony, he can make plants grow. Only his mommy Pinkie and his aunt Maud can tell him apart from the real deals when he plays masquerade like this. Even little foals like Sweet Apple Acres’ youngest Pumpkin Sweet can be perfectly emulated by Moosie in masquerade, size and everything. But Mousse never lets anypony see him don these costumes; a master of disguise never reveals his secrets~
 
Although Mousse is generally a rather upbeat pony, he does have episodes where he will be far more active and extroverted than usual, even topping his Mommy Pinkie as a baseline for these manic episodes. His forelock, which normally covers both his eyes, parts to reveal his bright-blue left eye during these times, although that eye is often bloodshot from lack of sleep and caffeine to stay awake. His productivity as a costumer skyrockets during this time, but he often draws concerns from friends and family because of the sleep deprivation and lack of proper nutrition. Often but not always, these episodes are followed by a depressive period, when his colors dull, his mane and tail lanken, and his blue eye is covered to make way for his right eye, blood-red with a piercing yellow pupil. In these times, he spends as much as entire days simply laying in bed doing nothing. The most anypony can prompt out of him in these times is a morose lamentation of how useless he and his costumes are. It is impossible to predict when these episodes end.
 
As a newborn colt, Mousse’s eyes were constantly closed. He only apparently opened them when his forelock grew long enough to cover them. Nopony has ever seen both of his eyes at once, not even his mothers or sister or closest friends. Growing up, Mousse always loved the act of playing dress-up. He was always eager to be Momsy Rarity’s model for her filly and colt lines of dressware, and she was always happy for his eagerness, although he often volunteered for outfits far too large for him. Pinkie adored this in her son, though.  
Mousse refers to Pinkie as Mommy, Rarity as Momsy or Mother, and Rainbow as Ma.
 
Mousse’s coat comes from a blend of Pinkie’s mane color from the color of his grandmother Cookie Crumble’s coat. His mane is a mix of his grandfather Magnum’s mane and the pickaxe handle in his other grandfather Igneous’s cutie mark along with Igneous’s coat outline. His right eye is a combination of Rarity’s cutie mark and Pinkie’s party canon, while his left eye is taken directly from Pinkie’s “YOU PINKIE PROMISED!” moment in The Last Roundup.
 
The rainbow streaks in his mane and tail, huh? Well, Moosie and the other children of the Mane Six from Friendship Is Magic bear the mark of the Rainbow Power their mothers earned from the Tree of Harmony. The colors come from the coat colors of each of the Mane Six. Depending on his mood, Moosie feels like he is quite capable of magic towards great harmony when he is close to his sister and the other two children of the Mane Six, but there is just something missing there. Do they need six to do this…?
 
His moms Rarity & Pinkie were a strange match to so many in Ponyville; how could a prim and proper diva like Rarity possibly fall in love with a raucous and unrefined mare like Pinkie Pie? Friends was already kind of stretching it. But anypony who could see them together knew that a purer love could not exist. Rarity fell in love with Pinkie that day she helped reproduce her favorite book from her fillyhood, as bizarre and almost grating that day was. As Pinkie said, the smoothie stain was another way to remember they day she fell in love . It’s harder to guess when Pinkie fell in love with Rarity; maybe she always loved her, even when she was infatuated with Rainbow Dash? It’s always hard to guess with Pinkie Pie; she can be as hard as a jawbreaker one moment and as pliable and stretchy as rubber the next. But it was during their visit to Manehattan to help Rarity pick out a locale for her new boutique that they realized they were in love, and their follow-up visit to help out Saffron Masala and her father that they first dated. They were the first of the Mane Six to officially seal the deal as a couple, even before Rainbow Dash & Fluttershy who’d known each other far longer.
 
———
 
Since my Duchess Skystar was uploaded here, I decided to get on with uploading the rest of the Friendship Is Magic: The Next Generation cast.