As of 1 January 2017, here's a list of NPC allies in the game:

Adam Jensen – protagonist from Deus Ex: Human Revolution
A man with short brown hair who wears all black with a dark grey coat. He has several augmentations, including metal arms. He looks at the battlefield and says, 'I never asked for this...'
Albus – supporter from the Castlevania game series
A young man who is also a member of Ecclesia. He wields the magical gun named Agartha.
Alucard – protagonist from the Castlevania game series
A tall man with long silver hair dressed in a black outfit with a black cape and wields the Alucard Sword. The half-vampire son of Dracula.
Artea – protagonist from the Lufia game series
An elf with blue hair that wields a powerful bow.
Arucard – protagonist from the Hellsing manga series
A tall man with short black hair dressed in a dark grey suit with a red overcoat, white gloves, a large red fedora and circular sunglasses with an orange tint. Formally known as Dracula, he is perhaps the strongest vampire in existance.
Ash Williams – protagonist from the Evil Dead movies
A man who works in the Housewares section of S-Mart. He wears a blue shirt, dark brown khaki pants, and brown leather boots. He wields a boomstick in his left hand and has a chainsaw attached to his right hand. "Groovy."
Bayonetta – protagonist from the game series of the same name
A woman with a very tall figure who wears a black outfit. She wields four guns, one in each hand and one attached to the rear of her high heels on both feet.
chaos – protagonist from the Xenosaga game series
Appears to be a young man with white hair and a dark tan. He wears a dark blue shirt, white pants, a blue and yellow vest and gloves of the same color. He looks at the battlefield and says, "I guess there's no choice but to fight..."
Chun-Li – from the Street Fighter game series
An agent of Interpol. She has brown hair, wears a blue chinese dress with a gold trim, white boots and large bracelets with spikes on them.
Cloud Strife – protagonist from the Final Fantasy game series
A young man with spiky hair and wears the SOLDIER outfit. He wields the Buster Sword weapon.
Curry Man – from WWE
A man who wears a red and yellow outfit in a flame design, along with a mask that has a decorative plate of curry on top. "He's hot! He's spicy! He tastes great! Curry Man!"
Dante – protagonist from the Devil May Cry game series
A tall man with white straight hair and a long red trenchcoat. This is the brother of Vergil, the trickster Dante.
Dart Feld – protagonist from The Legend of Dragoon
A young man who wears red armor and a red bandana. He wields the spirit of the Red-Eyed Dragon.
Dekar / Hydekar – protagonist cfrom the Lufia game series
A tall man with spiky dark purple hair who wears black armor, along with a sword and shield. In addition, he can use a variety of weapons. He looks at the battlefield and says, "Fighting random monsters in an arena is the second best thing I'm good at!"
Misaomaru 'Don' Kanonji – supporter from the Bleach manga and anime series
A spiritual medium. He wears sunglasses, a silly looking hat and a long cape. He's Karakura-Raizer: Spirit. And probably the most useless ally you can take into battle with you!
Dovahkiin (the Dragonborn) – protagonist from The Elder Scrolls V: Skyrim
A rare individual born with the blood and soul of a dragon but has the body of a mortal. A natural master of the Thu'um, otherwise known as Dragon Shouts.
Fi – supporter from The Legend of Zelda: Skyward Sword
The humanoid representation of the Master Sword, the spirit within the sword. She is half purple and half blue with a large blue diamond in the center of her chest. She radiates light energy.
The French Taunter – antagonist from Monty Python and the Holy Grail
The leader of the French Knights who taunts everyone.
Frog
A four to five foot tall frog who currently wields the powerful Masamune sword.
Guy – protagonist from the Lufia game series
A tall man with blonde hair who wears black clothing with silver armor on top. He wields a large axe in battle.
Guybrush Threepwood – protagonist from the Monkey Island game series
A clumsy looking man with blonde hair, the start of a blond goatee, a blue and red, buttoned-up jacket, boots and a large belt with a belt buckle that has his initials on it. He is Guybrush Threepwood, Mighty Pirate (tm). Insult Sword Fighter extraordinaire.
Harry Dresden – protagonist from The Dresden Files
A tall man with brown hair. He wears all black with a dark brown duster and a dark brown hat. He carries his trusty staff with him.
Hrist – supporter from Valkyrie Profile
A legendary Valkyrie that wears black armor with a white skirt attached to it. She will not hesitate to attack her 'allies' if they get in her way.
Ichigo Kurosaki – from the Bleach manga and anime series
A young man with bright orange spikey hair and is wearing Shinigami robes with Zangetsu strapped to his back.
Indiana Jones – protagonist from the movie series of the same name
A the well-known archaeologist. He wears a brown shirt, dark brown pants and boots. He also has a black leather jacket, a leather whip and his iconic dark brown fedora.
Iori Yagami – from the King of Fighters game series
A tall man with red hair who wears a black shirt and red pants. He looks at everyone and simply scoffs.
Jimmy the Dwarf – from the Dwarves vs. Zombies Minecraft event
A weak dwarf under the service of Old Man Willakers. The Old Man calls everyone Jimmy, regardless of their actual name or gender.
Jin Uzuki – from the Xenosaga game series
A man who wears a green and white outfit and carries a katana in hand. He is Shion Uzuki's older brother.
John Cena – from WWE
The 15-time WWE World Heavyweight Champion and the face of the company. He stands for Hustle, Loyalty, and Respect.
Judge Dredd – from the movie of the same name
A tall man wearing the standard Judge uniform and a helmet that covers most of his face. He is the Judge, Jury, and Executioner. He looks at the battlefield and says, "I am the law!"
Juliet Starling – protagonist from Lollipop Chainsaw
A young woman with blonde hair and wears a purple San Romero Knights cheerleader outfit. Additionally, she is a zombie slayer who wields a large chainsaw that is pink with hearts on it.
Julius Belmont – protagonist from the Castlevania game series
A man who is the latest warrior in the Belmont family line to wield the Vampire Killer whip and perhaps is the strongest Belmont.
Kaien Shiba – from the Bleach manga and anime
The former Lieutenant of the 13th Division of the Gotei 13. He wears the standard Shinigami outfit and has a tattoo of the Shiba family crest on his arm.
Kain Highwind – protagonist from the Final Fantasy game series
A tall man that is a friend of Cecil. He wears dark blue and black dragoon armor along with a helm that is designed similiar to a Dragon. He is a highly-skilled Dragoon.
Kaylona
A holy cleric. She is wearing a flowing white robe, wielding a Mace, and shield. She is ready to keep her fellow Allies fully healed.
Ken Masters – from the Street Fighter game series
A man with medium length blonde hair who wears a red gi. He also wears a black belt and red gloves.
KOS-MOS – supporter from the Xenosaga game series
A female android with red eyes and long blue hair. She wears a mostly blue and white outfit, along with a large blue and white visor. She analyzes the battlefield and says, "Eliminating enemy threat."
Ky Kiske – protagonist from the Guilty Gear game series
A handsome young man with blond hair in a ponytail and blue eyes. His usual outfit is a loosely-fitting, blue base version of the white dime-a-dozen Sacred Order of Holy Knights (aka, the Holy Order) Uniform, fastened together by a white belt buckle.
Lara Croft – protagonist from the Tomb Raider game series
A a British archaeologist and well-known Tomb Raider. She has long, brown hair that is braided into a ponytail, and wears a sleevless green shirt, brown shorts, black gloves, and brown boots.
Lenneth – protagonist from Valkyrie Profile
A legendary Valkyrie who wears blue armor with a white skirt attached to it. She is skilled in the use of swords and bows.
Lightning – protagonist from Final Fantasy XIII
A young woman with long pink hair who wears a modified Guardian Corps uniform. She carries her Blazefire Saber gunblade in hand.
Link – protagonist from the The Legend of Zelda game series
A tall Hylian wearing a bright green hat with a green tunic. In his left hand he is holding the ancient and powerful Master Sword while a Goddess Shield is in his right. This is the Hero of Time that legends were written about.
Maat – supporter from Final Fantasy XI
An old man who is a master of martial arts.
Magus
A tall man with long purple hair, long ears, and weas a red cape over his armor and clothing. The man also carries a large scythe in hand as well.
Maria Renard – supporter from the Castlevania game series
A young girl with blonde hair who wears a pink and white outfit. She fights with the power of the four sacred beasts.
Mario – protagonist from the Super Mario game series
A plumber with a large bushy mustache wearing a blue long-sleeved shirt with red overalls over it and a red hat with an "M" on it. He looks at the group and goes "Hey paisanos!"
Maxim – protagonist from the Lufia game series
A man with red hair who wears light blue armor. He carries the powerful Dual Blade sword in hand.
Mega Man – protagonist from the game series of the same name
A short robot that is blue in color. Created by Dr. Light to defend the world against the evil Dr. Wily.
Mega Man X – protagonist from the game series of the same name
A taller version of Megaman and is also blue in color. He is the final creation of Dr. Light.
Midna – supporter from The Legend of Zelda: Twilight Princess
A tall Twili and the Twilight Princess, the ruler of the Twili race. She wields the powerful Mirror of Twilight in battle, and can summon a dark green fist to attack her foes.
Mr. Satan – from the Dragonball Z anime series
A man with a large afro, large sideburns, a horseshoe mustache and giant muscles. He wears a dark brown dogi shirt, with a white belt wrapped around, white pants and black boots. The Earth's so-called "Greatest Champion!"
Bruce Willakers (or Old Man Willakers) – from the Dwarves vs. Zombies Minecraft event
Bruce is a legendary Dwarf with incredible power and a long white beard. While he might be an old man, don't let his age fool you! He looks at the battlefield and says, "Drink your juice, Jimmy, and fight the monsters! Also, stay away from me or I'll death stare you!"
Orihime Inoue – from the Bleach manga and anime series
A young woman who is a friend of Ichigo Kurosaki. She enters the battlefield to provide support for the Allied Forces.
Orphen – from the manga and PS2 game of the same name
A young man with brown hair who wears a dark grey shirt with black pants and a black vest. He also wears a dragon necklace around his neck. He is a powerful magic user, though can be lazy at times.
Pac-Man – from the arcade game of the same name
A big round yellow ball with red boots and brown gloves on his hands. He loves power pellets (:V)
Prishe – supporter from Final Fantasy XI
Appears to be a young Elvaan female with long lavender hair, pointed ears and blue eyes. She wears black shorts with a black top and frilly purple sleeves, along with tan boots.
Rare Akuma – from M. U. G. E. N., based on Akuma from the Street Fighter game series
A fighter with red hair and a gray dougi on. He is Gouki, the strongest fighter and is said to be a great demon.
Richter Belmont – supporter from the Castlevania game series
A man with brown hair who wears a blue shirt and white pants. A powerful member of the Belmont family that wields the Vampire Killer whip.
Robocop – protagonist from the movie and TV series of the same name/dt>
A cyborg cop in silver and black armor. He carries his large Auto9 gun in hand. "Dead or alive, you're coming with me, creep."
The Rock – from WWE
A tall man with a dark tan and a tattoo of a bull on his right arm along with a large Aztec tattoo that covers his left shoulder, arm and part of his chest. The Rock enters the battlefield and shouts, "Finally, The Rock, has come back to the Battle Arena!" A wrestler
Rose – supporter from The Legend of Dragoon
A mysterious woman who wears dark purple armor that has a gold trim. The wielder of the Darkness Dragon spirit.
Gaignun Kukai Jr. (Rubedo) – from the Xenosaga game series
He appears to be a kid who wields two handguns in battle. While he appears young, he is actually older than what he seems and can be quite powerful.
Rukia Kuchiki – from the Bleach manga and anime series
A short young woman with short black hair and is the current Lieutenant of the 13th Division of the Gotei 13 and is also the younger sister of Byakuya Kuchiki.
Ryu – from the Street Fighter game series
A man with medium length brown hair and wears a white gi along with a black belt. He also wears red gloves and a red bandanna.
Ryudo – from Grandia II
A young man who wears a dark blue outfit. His companion is a talking bird named Skye, who stays by his side.
Samus Aran – protagonist from the Metroid game series
A tall woman with blonde hair who wears a Chozo power suit that is red and orange in color. Known to the Space Pirates as "The Hunter."
Selan – protagonist from the Lufia game series
A young woman with blue hair who wears a white oufit. She wields a sword and staff in battle.
Shanoa – from the Castlevania game series
A young woman who is a member of Ecclesia and a powerful user of magical glyphs.
Shantotto – from Final Fantasy XI
A Tarutaru who wears the Black Mage AF armor, excluding the hat. She is well-known in Windurst and one of the strongest magic users in Vana'diel. She is also very arrogant! "O~hohohohohohoho!"
Simon Belmont – protagonist from the Castlevania game series
The legendary Vampire Hunter and a strong member of the Belmont clan. He is a master with the Vampire Killer whip.
Sol Badguy – protagonist from the Guilty Gear game series
A tall man with brown hair and golden eyes with slit pupils, wearing a tight, black undershirt with the top half covered by a red, sleeveless jacket along and white jeans. His wears a red headband along with a pair of black, fingerless gloves, red shoes, a drape of red cloth hanging down beneath his buckle and a multitude of belts.
Solid Snake – protagonist from the Metal Gear game series
The legendary mercenary. He is a tall man with short brown hair and wears a dark gray stealth suit. He also has a gray bandanna on his head. He looks at the battlefield and says: "Kept ya waiting, huh?"
Soma Cruz – protagonist from the Castlevania game series
A young man with white hair. He wears black clothes along with a white and silver coat.
Son Goku – from the Dragonball Z anime series
A Saiya-jin who was sent to Earth as a baby. He wears an orange dougi over a blue shirt and has black hair.
Squall Leonhart – protagonist from the Final Fantasy game series
A young man with brown hair who wears a white shirt, black pants, and a black coat. He has a silver chain with a Greiver pendant on it as well. He wields a gunblade in hand.
Sui-Feng – from the Bleach manga and anime series
A short, young woman who is the 2nd Division Captain of the Gotei 13 and current Commander-in-Chief of the Onmitsukidou.
Terry Bogard – from the King of Fighters games
A muscular man wearing a white shirt, blue jeans, a red vest with torn sleeves and his trademark baseball cap. He grins and gives a thumbs up!
Tia – protagonist from the Lufia game series
A young woman with long purple hair. She wears a pink dress and uses a whip as a weapon.
Urahara Kisuke – from the Bleach anime and manga series
A tall man with light blonde hair. He wears a dark green shirt and pants, along with a black coat, wooden clogs on his feet and a bucket hat with green and white stripes.
Vash the Stampede – protagonist from the Trigun game, manga and anime series
A tall man with bright blonde hair that spikes up. He's wearing yellow-tinted sunglasses and a bright red coat. His gun, Peacemaker, is in his right hand while a donut is in his left hand. "Can't we settle this with some donuts?"
Vyse – from Skies of Arcadia
A young man with brown hair that is a member of the Blue Rogues. He wears a blue and black outfit and uses two swords in battle.
Genryuusai Shigekuni Yamamoto
An old Shinigami who is the Captain of the 1st Division and the Captain Commander of the Gotei 13. The oldest and strongest Shinigami who also carries the powerful Ryuujin Jakka zanpakutou.
Yoko Belnades – from the Castlevania game series
A woman with long blonde hair that is a member of the Belnades clan. She wears a red and black outfit.
Yoruichi Shihouin – from the Bleach manga and anime
A woman with dark skin, long purple hair and golden eyes, dressed in a black sleevless shirt, black pants, white shoes and an orange coat. The former 2nd Division Captain of the Gotei 13.
Yuushirou Shihouin – from the Bleach manga and anime
The younger brother of Yoruichi Shihouin and the 23rd head of the Shihouin Clan.
Zero – protagonist from the Mega Man X game series
A robot who wears red and white armor with blonde hair and wields a powerful beam saber in hand.