Moon Sugar was a drug. Skooma was a drug. What the Housecarl didn't know was her Thane's apparent love for catnip.
The Housecarl had dried some catnip to make tea for herself after a night of drinking mead and celebrating the killed dragon in Dragonsreach. She had left her Thane's Breezehome to go get water from the bucket they always kept out back when she entered the house to find a hilarious sight.
The awe-inspiring, fearsome Kahjiit Dovahkiin was rubbing her face on the floor where scattered bits of catnip lay. The Housecarl watched her noble Thane grab a piece and rub it on her face, inhaling deeply.
Lydia quietly set down the kettle full of water and began picking up the crunched leaves. She continued quietly until a clawed hand slapped her hand, sending all the catnip fluttering away.
She giggled ferociously when the Dragonborn began chasing the leaves like a common house cat with a moth. Almost incomprehensibly, the Dovahkiin was suddenly invading her personal space, sniffing at her neck and her clothes before rubbing her face all over Lydia's armor, leaving behind tufts of shedding fur.
Then she pulled away, leaving her paws on Lydia's lap but saying with wide eyes, "You realize this one has whiskers and… a… a t-tail?"
Lydia just about died laughing when the Dovahkiin began chasing her tail.
She would make sure to slip some more into the food the next time it was her turn to cook on one of their silly adventures.
Lydia had a small cat as a child. The small child was so afraid it would run off, she kept it indoor most of the time. Occasionally, when it would see something tantalizing outside the window, its teeth would start clacking. As Lydia grew to the hard warrior she was now, the cat died, and was eventually forgot about.
Her memory was jogged when they were raiding a bandit camp one night. They had discovered a dog-fighting ring, it seemed. After the humans were dead and only two dogs remained in cages, Lydia heard a low, terrifying mrrowlll that seemed to be from a demon's jaws. It was quickly answered with a long howl.
Then the Khajiit started chittering at the wolf. Lydia gritted her teeth as one of the smugglers yelled, "Who's there?" Inwardly, however, she smiled.
After only a few months of travelling all across Skyrim, Lydia found her Khajiit to be two things. Neurotically clean and very subtly vocal.
Every time they made camp or paused for a break, the Dragonslayer would run her furred paws over her ears, or would nibble out a speck of dirt from between her pads. She would pull out fur that still clung to her, but was not actually attached. Once day, she asked the Dovahkiin why.
"Khajiit good hunter," She answered quite simply.
"I am a good hunter," Lydia corrected politely, "What does that have to do with being obsessive about grooming?"
"This one must have no strong smell so that prey will not smell. I do not wish to smell like Whiterun. Smell like herbs and sweat. Too strong, prey notice."
Lydia did not pursue further, but she personally held the opinion that the Dovahkiin had ticks.