Also, she was not born a man.
In case you'd been wondering.
"Years ago, when I first started acting, everybody was a size 1 and 2 at that time," Lopez told Andy Cohen on Thursday's episode of "Watch What Happens Live."
"So me being a size 6 was like, whoa! That's like, wow!"
The "Boy Next Door" star revealed her reality during those booty-licious days: "I used to go between a 6, an 8 and a 10 all of the time, 'cause I'd gain weight and lose it and whatever. And that was, like, I had the hugest butt in the world.
"Now it's like small potatoes compared to some of this
Lopez also revealed -- possibly for the first time -- the weirdest false rumor she's ever heard about herself.
"One time this makeup artist brought an article ... about the fact that I was actually a small Guatemalan man, and how I transformed myself into 'J. Lo,'" she said on the "WWHL" after show, slapping air quotes around her nickname for emphasis.
"It had a detailed description of the surgeries that I went through, including something to make myself taller," Lopez said. "The whole wig and painfully putting each hair in. It was crazy. It was bizarre."
She swore this really happened. "He showed me the article," she said. "I read it myself.