What’s this? A chance to infodump worldbuilding for some tiny fantasy stuff? Ohohoho!
The mouse is Noble Dandelion, Holy Knight of Our Lady Of Grain! (Noble is their personal name, Dandelion their family name. Their siblings are Brave, Vivacious, Wistful, and Bitter)
Noble’s from an entire species of sapient mice who live in a fantasy world, alongside stuff like dragons and elves and regular non-sapient mice (to who they resemble, but are quite biologically distinct), and while there’s a variety of “steeds” her people utilize, Chickens are useful mounts because they’re reliable, take to training, breed well (plus you get eggs out of the deal)…and will absolutely eat your enemies when it comes down to it.
But first, you have to control them so they don’t just eat you instead.
Her hen, Toast, is from a domesticated breed and was raised as a riding animal, so Toast is already predisposed from a long line of chickens that’ve been selected for less eating-mice-atude (and probably altered a bit with magic, to boot) and trained since hatching to wear little saddles and be steered around. I haven’t thought much about specific mousefolk-engineered riding chicken breeds yet but I’ll probably hyperfocus on that eventually!
(A fun related fact: a lot of creatures like cats and foxes and other predators have a slight instinctive aversion to beings like mousefolk and ratfolk- though predation still is a very real and not uncommon danger, as a result of generations and generations of cats finding out that if you try to eat a pixie you WILL know regret, because that pixie is going to come back and cast spells on you for the rest of your nine lives. A mouse? A delicious snack. This thing that looks like but does not smell like or act like a mouse? Oh shit! It has a spear!!!!)
Naughty Chickens are resigned to pulling carts in a muzzle and blinders or slaughter. Sometimes they’re just sold to bigfolk since humans are always willing to buy more chickens, or they may be sacrificed to threats like dragonets or awakened cats in exchange for the safety of mousefolk towns. Communities with individuals who can control animals through magical means might keep more aggressive birds around as protection from outside threats. (Some mousefolk and ratfolk cultures also engage in basically high-stakes jousting with fighting roosters which is exactly as nightmarish as it sounds)
Cheering Dawn, however, Noble’s Rooster, is a feral rooster, more junglefowl than domesticated by any hands, and he was very, very intent on eating her initially.
Slay if you must, tame if you can, the beast terrorizing the fields, or join the cycle of death and life trying.
She basically underwent a trial by fire to prove herself as a holy knight by basically riding Cheering Dawn without getting devoured like someone may break a horse to exhaustion, if that horse wanted to eat you, and then calling upon a blessing from her Goddess to bind him to her as a Knight-Steed. Magic helped a lot. Not to say it still wasn’t quite a bit of training needed afterwards, and he certainly didn’t LIKE her for a good long while even if he was incapable of directly harming her, but with enough treats and the opportunity to have sick metal talons with which to attack enemies and subsequently devour them, he becomes a reliable steed.