당신 know, 보컬로이드 are basically collections of notes that 당신 can string together to produce music...but the mascot characters on the boxes have personas of their own.
Of course these aren't official, but this is just my perspective based on their vocal styles and what 팬 have made them out to be. Enjoy!
(NOTE: Some of these are kinda harsh, but it's just for comic relief, so lighten up ^.^)
Miku Hatsune: Cheerful, fun-loving and charismatic. She tries to avoid fights, but will never back down if dragged into one. Kinda childish and a drama queen, but has a good heart.
Rin Kagamine: Moody brat who is secretly really sweet. Likes tangy foods. Loves to prank people. Possibly a little bipolar. When somebody messes with her loved ones, she goes into full-on rage mode.
Len Kagamine: Clueless and childish. Gets excited about 음식 and animals. Shy piece of trash; is cute, but won't admit it. Lovable. He is actually really deep and philosophical, but the instant he realizes he has a point, he totally forgets everything he was about to say.
Meiko: Drunk a lot. Rarely serious, but occasionally goes off about gay rights and animal equality. Really smart, but lazy. Super seductive. Mom friend, dad jokes.
Megurine Luka: Never smiles. Is bluntly honest about everything. She met Miku at a young age, and she just started following her around everywhere, so Luka just goes with it. Likes fish. Has a soft spot for animals, and occasionally develops strong feelings and passion for some things.
Kaito: Innocent af. Likes ice cream. Doesn't know what porn is.
Gumi Megpoid: Sweet girl, but a pyromaniac who will suddenly rant about pain and despair, then immediately behave normally again. Eats a lot of vegetables.
IA: Beautiful soul, beautiful voice. A big bundle of hate. Likes Cheerios and cats.
Lily: Doesn't take your shit. Likes 사워, 사 우 어 things; is sour. She's pretty and she knows it. Secretly a cream puff.
Kokone: Doesn't go anywhere without her scarf, even in 90 degree weather. Nice to everybody. Gets a new crush every few days. Is color-blind and clumsy af, but tries hard anyway.
Gakupo Kamui: He is weird, but he embraces it. Is a transvestite who has always wanted to be a samurai warrior; low-key gay for Kaito. Likes Avril Lavigne.
Oliver: Cinnamon roll, too good for this world. Deadly chef. Allergic to everything.
Fukase: Crazy psychopath, but somehow hotter than the flaming pits of purgatory. Can make pancake art. Hisses at the sunlight.
SeeU: Adorable, but too dense to tell if somebody is flirting with her, making her even cuter. Has a new hairstyle every day. Can't decide what to drink at breakfast every morning; always late to everything.
CUL: Flirts without realizing it. Has a minor case of OCD; horny all the time, but never cheats. Low-key badass.
Anon: Can't focus on anything except music/sketches; super clumsy. Her boobs always get in the way. Hyperventilates about everything.
Kanon: Loves to eat, but never gains weight. Really smart without trying. She's nice, but she has a big mouth, so people hate her anyway. Can never make decisions.
Nekomura Iroha: Loves cats. Is a cat. Cannot stand 게, 크랩 meat. Doesn't know how to flirt. Good at math; occasionally roasts her friends, but the roasts are bad 80% of the time.
Yuki Kaii: Cute.
SF-A2 Miki: Spite is her greatest motivation. Never does anything right simply to annoy you. Makes comic book references on a daily basis. Extremely picky.
Mayu: Sweet one minute, will rip your face off the next. Likes stuffed animals. Cuts herself for attention. A really good person deep down, but also a crazy bitch.
Yuzuki Yukari: Really pretty, but nobody notices (including her) because of her cold personality. Good at everything. Socially awkward, but can be sweet if 당신 speak with her alone. She likes to write songs and 시 about depression to foreshadow her own pathetic life.
Galaco: Princess Bubblegum.
Mew: Catwoman; sweet but totally goth. Complete badass.
These are the ones I could think of. If 당신 can recall any I might have forgotten, please let me know and I will add them asap. Thanks!~