“Katy was due to be the star guest on Chris’ show. But he got a call from Russell late the night before telling him Katy wouldn’t be appearing as they wanted to spend the evening together,” a entertainment mole tattles to The Sun Wednesday. “Chris was a bit annoyed but thinks Katy is hot as well – and if she was his girlfriend he would probably do the same!”

“They’s completely fallen for each other,” an alleged friend of Russell’s spilled to The Mirror over the weekend.

“Katy’s just the girl to keep Russell on his toes and he’s completely head over heels for her. He keeps telling us he’s never met anyone like her and he knows she’s the one for him. He’s 34 now and has been playing the field for years now and he’s thinking this could be the time to settle down and maybe think about starting a family,” the friend added.

Gym Class Heroes star Travis McCoy, who dated the “I Kissed A Girl” singer on and off for more than three years, is reportedly green with envy that Katy is now romancing renowned womanizer Brand — the Forgetting Sarah Marshall star has previously admitted to struggles with alcohol and sex addict.

A source blabs to The Mirror: “He’s livid, but getting a sick kick out of the idea their relationship will go under due to Russell’s philandering.”

The “I Kissed A Girl” singer is worried her evangelical Christian parents won’t approve of her whirlwind romance with the British comedian – a famed womanizer with a history of alcohol addiction – but thinks meeting him could change their mind.

Katy and Russell were first romantically linked after the MTV Video Music Awards when they were seen kissing at Lady Gaga’s VMA afterparty at New York nightspot Avenue.last month. The pair then enjoyed a romantic vacation in Thailand and were spotted watching shows at Paris Fashion Week.

The 24-year-old singer’s parents, Keith and Mary Hudson, are pastors and run a ministry near Los Angeles.

“Keith and Mary are devoted to the church and hold the institution of marriage as a central core of their beliefs,” a source tells Britain’s The Sun. “They are genuinely happy for their daughter, but want to give Russell the once-over to check that he is suitable.”

“Katy is as besotted with Russell as he is with her,” says an insider. “Katy is sure that, after they get used to him, they would approve of Russell, but she wants to get that initial meeting out of the way as early as she can.”

Katy hopes Russell, 34, will fly to Los Angeles to spend time with her family before her hosting gig at the MTV Europe Awards (EMAs) next month.

“It was cute…..And the best part is that Katy responded by sending him a topless photo of herself.”

Katy and Russell were first romantically linked after last month’s MTV Video Music Awards, when they were seen kissing at Lady Gaga’s after-party at New York City nightspot Avenue. Now snitching celebrity tattles claim the “Hot N’ Cold” singer was whisked away on a romantic getaway to Thailand after impressing Russ with a picture of her ample bosom.

“When they were both in New York for the music awards Russell finally got his chance to work his charm on her,” a source close to Katy told London’s The Sun on Thursday. “Katy knows his bad boy reputation but could not resist – especially when Russell sent her a love poem with a note attached saying, ‘Please send me a poem back,” says the insider.

“Russell couldn’t stop laughing when Katy sent a photo of her boobs with the word ‘poem’ scrawled across them. The next minute Russell picked up the phone and invited her to Thailand for a secret getaway.”

Friends have warned Katy, 24, about the 34-year-old comic’s womanizng ways, but after two bitter splits from ex Travis McCoy, of Gym Class Heroes fame, the star is determined to make this relationship work.

“Despite his reputation, Katy thinks Russell is so charming she just wants to give things a go with him. She thinks he is hilarious and incredibly sexy.”

The “Waking Up In Vegas” hitmaker was spotted locking lips with MTV Video Music Awards host Russell Brand at Lady Gaga’s VMAs afterparty at Avenue in the Meatpacking District — after the British comic joked onstage that he had the hots for the busty singing star.

“They were sitting very close together, flirting and whispering to each other with their faces very close. Then Russell leaned in for a long kiss. It didn’t look like this was the first time. He was looking extremely pleased with himself,” says a tattle.

The 2009 VMAs will air live from Radio City Music Hall in New York City Sept. 13 (9PM EST) on MTV.