We don't know who Jennifer Lopez is trying to fool that she and her ex boytoy Casper Smart aren't back together -- but it ain't us!

The former couple looked very much like a current couple when they celebrated Casper's 28th birthday at beloved Italian eatery Madeo after the MTV Movie Awards on Sunday night.

For the big night, the sexy mom of two donned a plunging black Versace jacket and skirt, while her younger companion opted for black jeans, a black shirt and a bomber jacket.

The 45-year-old singer/actress has insisted that the duo aren't back together and that she's "still single" -- but they just partied together at Hakkasan in Las Vegas on Friday, after getting back from a Mexican vacation with the actress' twins earlier in the week. We think the lady doth protest too much and these two are definitely back in full effect!

Earlier in the night, JLO stole the show at the 2015 MTV Movie Awards when she sauntered up to the stage to accept the prize for Best Scared-As-Sh*t Performance for her role in The Boy Next Door. The cast of Magic Mike XXL presented J. Lo with the award, and things got pretty funny when the actress tried to convince Channing Tatum, Matt Bomer, Joe Manganiello and Adam Rodriguez to dance for her.