LeAnn Rimes, Jessica Simpson Try to Act Sexy

LeAnn Rimes and Jessica Simpson seemed to put the past behind them on the set of their promotional ad for the Academy of Country Music Awards.

The country singers crossed paths years ago, when Simpson was dating Days of Our Lives star Jensen Ackles, who apparently cheated on her with Rimes.

Simpson called it her "first heartbreak" on an episode of Newlyweds. Rimes allegedly did some cheating of her own last week, as her affair with Eddie Cibrian, her hot co-star in Northern Lights, was exposed (if it's not a huge sham, that is).

But while shooting the promo video - which spoofs the NCAA Final Four - on February 11, the two goofed around while getting glamorous alongside fellow singers Kellie Pickler and Julianne Hough (yes, the Dancing with the Stars hottie).

"Jessica has a mouth guard, and I have an arm band," Rimes says. "It's really hysterical to see us try to walk and be sexy with all this basketball gear on!"

In the video, Jessica Simpson - whose fat pictures caused quite a stir earlier this winter - approaches Rimes, saying, "This is gonna be a big weekend!"

Rimes responds: "I know! We better start planning."

The ACM Awards will Sunday, April 5 at 8 p.m. Here's a look behind the scenes of the promo footage with Jessica, LeAnn, Julianne and Kellie ...