The Thai masseuse burst into the house wearing a fluorescent pink jumpsuit and golden platform boots - to boost her diminutive five-foot frame.
She told the others she had Cookie Power, and was so obsessed with the sweet treats she kept a jar of them with her at all times.
Kooky Kat, who emigrated to Britain from Thailand seven years ago,had the nation in stitches as she attempted to learn more English words, like "crotch" - spelled c-r-u-t-c-h - which she explained was a "boy sausage".
But despite being named the bookmakers' favourite to win the series, she soon became many of the housemates' most hated contestant.
The others frequently complained of her incessant singing and dancing, and began questioning whether her optimistic exterior was a facade put on for the cameras.
They accused her of pretending to struggle with her English vocabulary and even claimed she purposefully said things incorrectly for laughs.
Lisa spat: "She had a theme when she came in here. Cookie Power is a theme, it's not who she is".
When Kat burst into tears after Rex and Bex got into a heated argument, she came under fire for being overly sensitive.
Mario told her she was "unstable" and advising her to leave if she was going to weep every time there was a disagreement.
"It's laughable, the third eldest person in the house behaving like that," he added angrily.
But the 30-year-old managed to find a forever friend in housemate Rachel - and the pair united to take on the rest of the pessimistic housemates.
The duo decided they were the most "genuine" out of their fellow roommates, and speculated the others didn't like them because "they're jealous of how happy" they were.
In the zoo task, Kat and Rachel cemented their friendship by volunteering to share a two-headed llama costume for two days.
"I can do that because I'm very patient!" Kathreya declared, before asking aloud, "Does it mean we have to poo-poo together?"
And when Rex branded her Welsh gal pal "fake" and a "liar" after seeing her audition tape, Kat stood up to the bullying chef to defend her.
"Why do you care so much?" Kat challenged him. "Why do you have to be like that? I thought she was a very good friend. Why do you mind so much?
"People are now looking for a reason to dislike her," she added.
The Buddhist subsequently racked up scores of good karma when she managed to get her point across to the ever-arrogant cook. "I'll stop saying things," Rex promised.
And the chubby housemate - who once described herself as a "jacket potato" - did find an advantage to being deprived of cookies during her time in the Big Brother house - she lost several pounds.
"You have lost a lot of weight since being here," Rex told her.
"Now I'm a baby potato. A baby organic potato. But I still want to be skinny!" she cried.
But as the days went by, Kat's kind demeanour faded and she found herself in arguments with growing frequency.
She fought with Mikey during his reign as Head of House when he squirted water in her face as she dozed during the daytime.
Mikey claimed he had done the prank just for "a laugh" but Kathreya said she felt victimised: "Oh yes, I'm doing laugh as well," she said sarcastically.
"If you want to have a laugh with me, I'll have a laugh with you," she added, before deciding: "We don't play together, then. I don't think I enjoy it."
Mikey lat er claimed Kathreya had sparked the feud only to gain sympathy: "She showed how much of an actress she is today. She looked like the idiot."
On Day 71, she was ordered to jail with her pal Mohamed after they were caught discussing Rachel's nominations.
She was upset that she was sent to the clink just a day before Rachel faced eviction, but she was relieved when her best pal escaped getting the axe.
The pair was treated to a party in a disco next to the Diary Room, where they munched on grapes and cookies, as well as wine and lemonade.
"Thank you for letting me come in here," Kathreya beamed, after they hugged and told each other they love one another.
But the following days were to be filled with tears and arguments.
Kat cried after arguing with Darnell over Rachel's nominations of Rex, sobbing: "I feel lost. I really feel disappointed, sick, tired. I'm not very happy. I just want to go home now. Why you still doubt me? Why Rex and Mo still doubt me?"
And in the final week, she was in floods of tears again after Darnell and Mohamed joked they would evict Kat over Sara if they were given a choice.
But things are bound to look up now Kathreya has been evicted - she'll now have unlimited access to cookies!
