Collection of smaller, misc. thoughts
First, a simple thought: Jesper would LOVE bars of soap. I can't even say that he'd love them for the taste. I think he'd just have fun licking and chewing on it, looking all foamy and frothy like a rabid little fella. I don't think he'd eat them, though. Would just put it in his pocket where it collects dirt and lint, and continue licking at a later time. I feel like it'd be hard for Yarrow to discern whether or not Jesper is enjoying the soap, especially because I imagine he's wincing through his usual devious smile.
Jesper in an oversized sweater would be so precious. Long enough that his hands are hidden, and that it goes down to his knees. Mayhaps Yarrow's first few attempts at clothing for Jesper weren't the correct size. I like the idea that these could be comfy clothes or pajamas, or even like, it's laundry day and Jesper still wants to be dressed.
I don't think I've officially said it, it's not news, but Jesper is stumpy enough that his pants are sort of like shorts, too. I think with socks and boots on, they look more appropriately like appropriate length trousers.
When I was sick, I randomly got really into researching (and bought, sigh.) marbles. Primitive marbles are made out of clay and stone, but I still think Jesper collecting them would be sweet. Of course, he'd try to eat them, so I could see Yarrow putting them in a jar out of reach, that he could ask to play with under supervision.

I could see him having Kena get them for him when the wild imps visit Yarrow's home, and showing him his collection. I don't think they'd be particularly impressed, but they'd probably find it somewhat interesting. I could see Sol and Kena keeping an eye out, not for marbles, but for interesting rocks for Jesper. Maybe marbles if they steal from someone who just so happens to have them. (Not for the purpose of marbles, more like, the imps stole a satchel that happened to contain them.)
A few small things:
Sol likes to run around on all fours and affectionately headbutt Jesper and Kena.
Sol's inflection can sometimes sound child-like. When she says "okay", it will sometimes sound like "okee".
Jesper introducing kissing to Kena and Sol. Kena is initially adverse as it's a "person thing to do", but Sol, as usual, is open to the idea. Kena quickly becomes jealous of Jesper and Sol kissing on each other, and quickly changes his opinion.
I often envision Jesper essentially mounting Sol to nuzzle and kiss on her, but she is very small---Jesper makes sure to keep his weight off of her, and to cradle her in his arms in a way that doesn't interfere with her wings, but safely allows her to be on her back.
Although Jesper's claws are trimmed and not necessarily sharp, he is still much larger than the wild imps. Sol reminds him often to be very delicate with his touches, especially with Nona's newborn imp.
Sol explains to Jesper that after she was born, her mother immediately left the cluster with a few other older imps to start their own cluster. Sol survived thanks to an imp who had recently given birth and helped kept her fed. Ona, their leader, put Kena in charge of keeping her safe outside of the den. He's one of their fiercest warriors, so he initially felt as though having to guard her was a waste and more of babysitting duty. Over time, he chose to do it voluntarily.
Jesper asks about her father, but says that due to mating habits, she isn't sure if her father is still in the cluster or left with her mother. She goes on to explain most imps typically aren't aware who their father is unless mating stays in smaller bonds or specific circumstances.
Where my development is in present-day, is probably along the lines of Jesper having been a companion to Yarrow for about a year roughly. He met and befriended the local wild imps not long after meeting Yarrow, and is now bonded with Sol and Kena after several months.
By "now", I like to think that Yarrow is seen as less of a threat, and isn't discriminated against for being a "person".
Anyway... Ona, the elder of the wild imps, has never really had much interaction with Jesper. Most of his interaction have been with Sol and Kena and their secondary bondmates (Nona, Lon, Nia). Ona has given him a lot of permissions (mostly mating ((lol)), being invited to Sol and Kena's bond, staying the night, meeting Nona's baby), but trusts Sol's judgment mostly.
So, I was picturing that since it's been a few months, Ona wanted to speak to Jesper privately, which I imagine freaks him out thinking he's done something wrong.
Jesper: "Is in trouble with Ona?"
Sol: "No! Jesper is not in trouble! Ona just wants to talk to you!"
Meeting her for a private conversation, I could see Jesper with his head low, sitting down so that they're more eye level with one another. Ears low, eyes completely closed, looking ready to hear his punishment. I think Sol would actually be asked to stay and be nearby because he's just too anxious about what he could have done wrong.
I don't have specific dialogue in mind, and might have to update later if something comes to me, but she very politely tells him he's been of great help, has heard nothing but good things, and happy to have him.