Jennifer Lopez & Casper Smart

Jennifer Lopez and Casper Smart did NOT get back together, because we found out they were never really apart.

Sources close to the couple tell us ... the break-up they announced in June was a business move. Multiple sources say in the spring they did stop seeing each other, but only for a few weeks.

We're told JLo was hawking her movie, "Boy Next Door," and honchos on the film felt creating a buzz that she was hooking up with co-star Ryan Guzman would help sell tickets. It's hard to do that when you're not single.

But the decision wasn't one-sided. We're told Casper was up to the same thing because he was shooting "Street," a UFC fighter movie where he buffed up. Again, he was more appealing single.

It all makes sense now. Two months after they revealed their break-up, a photog got shots of them in a convertible BMW. When JLo saw the photog, Casper put the top up and she slumped down in the passenger seat, out of sight.

Then in December, a dog at Jennifer's house bit a neighbor. Turns out it was Casper's dog that did the deed and he came running out of the house in his pajama bottoms after the attack.

In February, Casper went to a GQ event, and when he left he walked down the block and jumped in a car JLo was driving, avoiding photogs. A few minutes later a photog saw them walk into a restaurant together. When they saw the guy they hightailed it inside.

And then they got bolder, dancing together at a Big Sean concert at the House of Blues in WeHo.

Case closed.

Not that Jennifer Lopez and Casper Smart have been fooling anyone -- but they're officially banging again ... and we're basing that on the fact they're finally swapping spit in public again.

Smart swung by "American Idol" Wednesday night to scoop up JLo and they kissed out in the open for everyone to see. They've been sprinkling clues for months -- slipping out of a GQ event together, partying at Big Sean's House of Blues gig ... and his dogs were at her house (which didn't end well).

They broke up last April after 2 1/2 years, but what if it was all for show?

J.Lo's insisted they're just friends, but after so much smoke ... this has to be a 3-alarmer.

Jennifer Lopez and Casper Smart are officially reuniting in court -- the woman who was bitten by one of Casper's dogs is suing both of them ... and her injuries are pretty graphic.

In the lawsuit, Andrea Ashley -- one of JLo's neighbors -- says she was getting out of her car back in December ... when Smart's boxer named Bear mauled her left arm and hand ... leaving her with broken bones and cuts. She's included photos of her bloodied limb in the suit.

Ashley says, right after the attack ... Casper walked out of JLo's house wearing only pajama bottoms and came over to apologize. That's interesting because Casper and Jennifer had broken up several months before the attack. As we reported ... J.Lo's people told us the dogs were only at her house for a visit with her kids. Apparently, Casper was visiting too.

Ashley says this wasn't the first attack -- Bear also escaped through a hole in JLo's fence and attempted to attack her in April. She says only her gardener saved her from getting mauled that time.

In the docs, Ashley says Casper called her, apologized, and offered to pay all of her medical bills. As for why she's suing Lopez ... Ashley says Jennifer bears some responsibility because the dog is escaping through her fence.

Further, she says Bear has remained at Jennifer's home since Jan. 8 ... and she's afraid he could get out again. Animal Control told us Bear was quarantined at Casper's home since the attack.

To hell with quietly hooking up ... Jennifer Lopez and Casper Smart don't seem to be hiding much anymore ... they were together again for a pre-Grammy date Saturday night.

J.Lo and Casper were spotted at Big Sean's Roc Nation shindig at the House of Blues where they were shakin' their booties and having a blast. Cool moment in the video -- Kanye on stage, shouting out Jennifer.

We're told the maybe-exes were hanging with pals Demi Lovato and Wilmer Valderrama.

Of course, they were seen out last Thursday night and even though they've been trying to avoid pics ... lately they seem less careful about slowing down the rumor train.

Jennifer Lopez and Casper Smart very quietly hooked up Thursday night, leading to the obvious question ...

Here's how it went down. Casper was out at the Z Zegna & GQ event in Hollywood where he hung out with Nick Jonas.

There are plenty of pics of Casper leaving the event with no sign of JLo. But we're told she was actually waiting in the car for him as he left.

They went to Hotel Cafe in Hollywood where this pic was snapped. It's the only pic of the 2 of them that was taken the entire evening.

They supposedly broke up in April, but they've been seen together from time to time, and they've taken great pains to avoid pics. Remember when she ducked down in her car?

And you may recall Casper's dog was at JLo's house recently when the dog bit someone.

Casper Smart's dog escaped from Jennifer Lopez's house and bit one of her neighbors ... leaving the woman with a broken hand.

Law enforcement sources tell TMZ ... Smart's boxer, named Bear was at JLo's home outside Los Angeles back in December ... when he got loose and clamped down on the neighbor's hand and arm.

Since the attack, Bear has been quarantined at Casper's nearby Woodland Hills home. Authorities are still trying to determine if the dog poses a danger to others.

We're told both of Casper's boxers still spend a lot of time at JLo's house ... since her kids love the dogs. It's unclear if JLo or Casper were at the house when the attack happened, but Animal Control gave Casper a citation for an unleashed dog ... since he's the owner.

Jennifer Lopez just massacred Marc Anthony, Ben Affleck, Diddy and worst of all ... Casper Smart!

JLo had a little truth slip on "American Idol" Wednesday night ... letting fellow judges Harry Connick Jr. and Keith Urban in on a secret -- she's awesome, but the problem lies with the men she chooses.

We forgot poor Chris Judd. She thinks he sucks too.

Jennifer Lopez and Casper Smart insist they're not back together, and Sunday night at the VMAs ... they went through great lengths to show they aren't ... which totally means they are.

As TMZ first reported, despite being photographed together last week ... her people swear they're leading separate lives and just friends.

So J.Lo and Casper walked the VMA red carpet separately, sat separately at the VMAs (except for a quick reunion for candy) and each showed up at Mastro's following the show ... but left separately.

Where there's smoke ...

Jennifer Lopez and Casper Smart REUNITED at the MTV VMAs ... if only for a quick second ... when the dancer made J.Lo an offer she couldn't refuse -- Skittles.

Despite the fact they were sitting in different sections, Casper made his way over to Jennifer's section during a commercial break with a sugary peace offering ... and the whole thing was captured on the VMA livestream.

As we previously reported, the two were spotted out together earlier this week -- despite the fact they recently broke up.

Casper Smart bought a sweet new pad in the San Fernando Valley and he WON'T be banging Jennifer Lopez inside ... these are the 2 things we know.

We found out Smart just closed on a $760,000 ranch-style home in Woodland Hills. He put down 20% -- $152,000. And get this ... it's all Casper's money. JLo didn't give him a penny. He's been renting out a condo he already owned and making money doing choreography for artists like Nicki Minaj.

The 2,039 sq ft house has 3 bedrooms, 2 baths, a pool, fruit trees, and a batting cage.

Now the banging part. We posted pics of Smart and JLo driving together Monday in L.A. and it looked like something was up -- she was trying to hide from the photog -- but we're now told they continue to be friends but the romance is over and out.

Plus ... JLO wouldn't be caught dead in THAT part of the valley.

Jennifer Lopez and Casper Smart were back together Monday ... and when she spotted the photog she ducked for cover -- which totally means they're banging!

We think it's JLo's car ... it's definitely not his, although he's driving.

JLo and Casper broke up in June after dating 2 1/2 years. There were reports Smart cheated on JLo with a transsexual, but he denied it and threatened to sue.

As we reported ... the breakup was amicable and they parted as friends. Now it appears there may be benefits to the friendship.

Casper Smart's post-Jennifer Lopez life may have fewer champagne wishes and caviar dreams ... but dude can still afford a (sorta) fancy new hair style.

Smart went full Asian on Tuesday ... strolling out of Philippe Chow while rocking a mean Samurai-styled topknot.

Casper was pretty talkative too -- giving us his pro-dancer review of J.Lo's recent twerkfest in Miami, but more importantly ... he told us what the hell he was thinking when he got his hair chopped.

Poor Casper Smart. No really ... poor Casper Smart, who went hat in hand to Bank of America.

As we previously reported ... Jennifer Lopez did NOT give Casper a fabulous parting gift -- such as money -- when the two broke up a few months back.

So the freshly single/cash strapped Casper made the trek to the Calabasas branch, spoke with a banker and then hightailed it out of the parking lot on his chopper.

It's unclear if Casper is serious about the place, but based on the location -- we're guessing he'll pass.

Dude already did more than 2 years on Lopez. Didn't end well.

Casper Smart's lawyer just got the most sarcastic letter we've ever seen in the 9 years of TMZ ... all stemming from Casper's alleged dalliances with transsexuals.

Casper's attorney threatened to sue TheDirty.com after 2 transsexuals posted comments on the website claiming they hooked up with Casper. The lawyer says the comments are defamatory.

But the lawyer for TheDirty -- David Gingras -- fired off a brutal response, telling Casper to pound sand. TheDirty's lawyer says if Casper has a case ... it's against the transsexuals, not the blog.

Here are some of the choice comments in the lawyer's response:

-- "In America, we have this annoying little thing called the 'First Amendment.'"

-- "First, your letter is addressed to 'Hooman Karamian' and yet it begins, 'Dear Mr. Hooman." I have no idea why lawyers think it's impressive to refer (incorrectly) to another person using their first name. I must have missed that class in law school. Do you think this makes you look smarter? Trust me -- not so much."

-- "Now let's get back to first year of law school, shall we? And to make this really easy for you …"

Casper's lawyer made the mistake of telling the lawyer for TheDirty this wasn't his first rodeo. So TheDirty's lawyer fired back, "You're darn tootin' Cowgirl -- this isn't our first time at the rodeo."

And check out the artwork next to the lawyer's John Hancock.

Them's fightin' words, cowgirl.