YA ofc!! I guess I probably don’t have as many as Olly since Olivia already has a lot of established canon info about her and I tend to even forget a lot of it sometimes because of that, but I’ve got a few!!
Half of these are for my post-canon AU btw!!! 😭😭

As I hc her and Olly as twins, Olivia is also his age range, being 16-19 mentally (though my human version has neared 17-18 for both of them). She’s brought to life shortly after Olly was folded, so she’s also a few days to a week old chronologically!
She’s also wasian (white/Japanese) like Olly!
Her gender’s the same, just a cis girl (or however “cis” you can get for origami).
She’s a lesbian. HUGE GIRL LOVER, but a lot of this is purely admiration as well.
She’s not the type to get into a romantic relationship, but she thinks girls are really pretty and would probably (fail to) flirt with them if given the chance. Gets super overwhelmed with admiration around women (semi-canon based off all her interactions with feminine characters in English LOL)
She wishes there were more girls in the world, but not just because she’s a lesbian. She also has a strong desire to do stereotypical girly things with other girls because it sounds fun to her
She would absolutely ask Birdo for her autograph if given the chance. Same goes to Rubber Band if it wasn’t causing all that trouble to the Toads and guarding the blue streamer.
She would also 100% see Peach as a role model and hang out with her often. Princess things!
She has a tendency to act like a strict mother towards Olly, despite being younger. She disciplines him frequently because she wants him to get better
She has a sibling-like relationship with Bobby; sees him as a best friend, but nothing more. I don’t like their ship anyway (sorry to half the fandom) </3
She’s very touchy with Olly (??? How do I word this in a way that doesn’t sound awful. I swear I mean this in a normal way). She’ll hug and grab and hold hands with him a lot, but she’s like this with a lot of people in general
She wants to learn a lot of things from Olly, especially more origami. Would definitely use that as bonding time!!
She sees cute things and asks Mario “Can we keep it?!” like finding a stray animal
She’s not all that innocent, just like in canon. She knows about more mature things, but that doesn’t mean she’s not embarrassed by them!! (Ex: Birdo/Mario scene in the Big Sho’ Theatre) (Only adding this despite being canon because so many people headcanon her as an innocent unknowing baby when that’s not really how she’s officially portrayed???😭)
She has a somewhat light, cute voice. A pretty generic anime girl voice with a hint of a princess-like nature, but lovable nonetheless!
A lot of people she comes across are enamored by her cute charm, but she’s mostly oblivious to it. The whole world loves Olivia.
^ Sometimes she will get special treatment or favors done for her because of this, like people offering to do errands for her or her always getting voted for in a contest.
She doesn’t love everyone back, though. While she finds the good in mostly everyone in the world, there are some folks she finds too irredeemable that it annoys her.
She doesn’t have a good grip on the concept of death, so sometimes she may suggest things that come off as sadistic towards enemies (like in the battles with the LoS).
While she seems pretty stupid in Mario’s world, she’s knowledgeable about origami as a “species/race” and wants to educate people on it when possible.
She loves getting her opinions in on everything. Even if it irritates someone.

THATS ABOUT ALL THE THINGS I COULD THINK OF ON THE SPOT THAT ARENT ALREADY COMPLETELY COVERED BY CANON… id love to hear anyone’s thoughts on my hcs for both the siblings 😈😈 and while i dont remember as much about the other characters (it’s been years since I’ve actually played the game in its entirety LOL i know im lazy but it’s a huge commitment and the game makes me sad bc it’s so tragic), you can always ask me for my hcs on them as well!!!! Most hcs are very old (i was literally 17-18….) but i can probably recall quite a few 😈😈😈😈 LMK!!!!! THANK YEW FOR THE ASK