The cat and the mechanic
Kaylee was ecstatic to have a cat onboard. Anything cute, fuzzy, and friendly was her kind of person. She'd never had pets when she was young. Machinery and animals was not the brightest combination in the 'verse.
Now that they had a pet, she was always doting on her. She spent money helping River get toys and fancy whatnots. They'd play with her in the cargo bay when they got the chance. Whenever River had to go on a job—which was rare, given her pilot status—Kaylee would watch over the cat. She'd brush her for hours and hours, talking and gossiping. After Inara left, she felt she'd lost a friend. She still had River, and now they had May.
One boring afternoon planet-side, Kaylee, River, and May decided to clean the engine. Of course, May was meant to sleep peacefully in the hammock, but she was too curious not to help. An accidental spill later, her fur was matted with engine wine and grease. Naturally, that called for a bath.
It sounded like someone was killing the poor thing. Mal heard it when they got back from their meeting. He ran to the source of the noise—May in the kitchen sink—and gaped at the torture bestowed on the feline.
"What are you doing to her?" he cried.
"Engine wine and grease have affixed themselves to her fur. The contents are not sanitary. We must lather, rinse, and repeat," River explained rapidly.
"We was cleanin' the engine and May tried to help!" Kaylee chuckled. "She's a real helpful cat, just mistook a step is all. She don't care for water much…"
May cried and Mal cringed. "I wouldn't like it much neither if two people were scrubbing all on me without me giving permission! Hurry up and finish. It's making things all sorts of not-quiet-like."
"Almost done, Cap'n. She'll be pretty as a picture. I think I got a ribbon for her collar!"
"Don't do that! She ain't gonna like it!" Mal snapped.
River raised her eyebrows. He quickly backpedaled, "Then she's gonna fuss some more and nobody's gonna sleep for her howling."
"Yes, Captain," River smiled. "We'll take care of her."
"See that you do, li'l albatross."
May meowed and he smirked, wandering off as fast as humanly possible.
"Cap'n likes the kitty," Kaylee hummed. "Cap'n likes the kitty's keeper even more."
"Kaylee!"
"Just sayin'."