Megan Fox & Brian Austin Green Totally On Again

While Transformers: Revenge of the Fallen was breaking box office records its opening weekend, star Megan Fox was on a double date in Las Vegas – with Brian Austin Green, not rumored new fling Shia LaBeouf!

Sources tell OK! the Palazzo Las Vegas was alerted Saturday morning that Megan would be arriving that afternoon.

Megan ended up missing her flight, but that didn’t halt her plans – instead she drove all the way from L.A. to Vegas, finally arriving at the Palazzo at 3 a.m. Sunday morning with her sister, her sister’s beau and Brian Austin.

According to a source close to the couple, this on-again, off-again twosome are totally switched on.

“Megan and Brian are definitely together. They call each other baby and are just so cute together. I don’t think they ever really broke up," says the insider. "They’re so comfortable and ridiculously cute. In the elevator Megan put on chapstick with her finger and then put the rest from her finger on his lips. They seem so happy together and so in love.”

The group slept in late on Sunday, an insider tells OK!, and then saw Cirque de Soleil’s Mystere that night. After the show the group went to vodka bar Red Square at Mandalay Bay for dinner and had drinks afterwards at Dos Caminos.

The source added, “You would never know she had the biggest movie of the summer out right now because she was so nice and humble, almost timid and shy.”