In the latest news from her "common sense is not so common" world tour, reports are flying that Rihanna, 24, has spent the past couple months hooking up with a certain very famous and fidelity-challenged actor.

So who's her new paramour?

None other than 'Two and a Half Men' star Ashton Kutcher.

Last week, the singer was spotted by tabloid photographers arriving at the 34-year-old Kutcher's California home around midnight -- and staying until about 4 a.m. And while some have insisted the two are "just friends," the wee hours of the morning aren't typically when "friends" have coffee and catch up. Especially when neither is known for java and chitchat.

So needless to say, this particular tryst sent tabloids into a frenzy -- including the ones across the pond. Britain's The Sun reports the pair met through mutual friends a while back, and have been secretly seeing each other ever since. A source said:

"The flirting began as soon as Rihanna and Ashton met and swapped numbers. That moved on to texts and arranging to meet. They snuck off to a Santa Monica hotel a few weeks ago. They are two single people having a fling, so thought it would be best to meet in secret."

Well, one of them is single anyway. Ashton's divorce from Demi Moore isn't yet final. The pair split last November after it came to light that he had at least one extra-curricular, um, "friend," which spelled the end of his seven-year marriage to the actress.

The Sun's source says Rihanna thinks Ashton is "funny and cute" but "they're too busy for anything serious just yet." And then in the same breath, that person reports, "She's starting to inquire about Kabbalah sessions with his rabbi." Because what casual hook-up doesn't involve religion?

The whole story is just the latest in a series of "seriously, girl, what are you thinking?" moments for the musical superstar. It wasn't that long ago that she was involved in a physical altercation with singer Chris Brown that left her bloodied and bruised -- yet as rumors swirled that they'd reconciled, she later gave a public and inexplicable statement of forgiveness and embarked on a two-song collaboration with him.