When Pete Wentz sat for a cover interview with Rolling Stone in February, he denied remors he was dating Ashlee Simpson, saying, "Maybe in a different universe, we'd be some hot couple, but not in this one."

A month makes a world of difference, it seems.

The singer, 22, and the 27-year-old Fall Out Boy frontman -- with whom she's been linked before -- enjoyed a recent hush-hush getaway to Mexico.

A Simpson source tells Us Weekly, "She really likes him."

The feeling seemed mutual on March 12 when they hit West Hollywood hot spot Hyde.

"He massaged her back and played with her hair," says an eyewitness.

Still, a source close to the rocker says, "they aren't that serious."

(Both stars' reps had no comment.)

Wentz and Simpson aren't the only ones hooking up this spring. Couples like Drew Barrymore and Spike Jonze, Ryan Reynolds and Jessica Biel, and Rachel Bilson and Hayden Christensen have also found romance this season. But who's likely to last and who's just a spring fling? Check out the new issue of Us Weekly for details on these cute new twosomes.