5:23 PM PT -- Ben Affleck was in a super chummy mood Sunday while out and about in his GF's home borough -- because he was actually interacting with fans ... something he hardly ever does.
TMZ got a hold of more video showing Ben going out for yet another smoke break while Jen was inside of Lit Bar doing her book thing. Sure enough, they'd drawn a noticing crowd ... but instead of cower away -- BA stepped up for a friendly chat, which proved hilarious.
Check out the clip -- you can see Ben chopping it up with these adoring onlookers, who were definitely star struck ... but who also kept their wits about them as they showered compliments onto the guy. Ben, of course, was gracious ... and pretty responsive.
We're told there was a bachelorette party next door, and that these ladies actually tried inviting Ben to the shindig -- but he duly noted, sorry ... "my girl" is inside, and I'm stuck.
He didn't say exactly that, but the sentiment was there -- seems these folks understand and then some. Let's hear it for the Bronx's MVP of the day!
3:59 PM PT -- Source close to J Lo tells TMZ … Jennifer and Ben went to a Latina-owned bookstore, Lit Bar, not far from where Jennifer grew up. She was there as part of her new mission-driven platform, Limitless Labs, to shine a light on Latina entrepreneurs and graduates of Goldman Sachs' 10,000 Small Business Program in time for National Hispanic Heritage Month.
We're also told Ben Affleck was proudly taping Jennifer when she talked about how important it was for her to be there in the community with all the entrepreneurs and David Solomon and Dina Powell from Goldman Sachs. Turns out ... Ben also spent time with the entrepreneurs and actually bought an armful of books.
Jennifer Lopez took Ben Affleck back to where it all started -- namely, the block that gave her her nickname ... and the dude seemed to make himself right at home by lighting up.
Bennifer returned to J Lo's stomping grounds Sunday -- this after spending the past few days in Italy, where they brought their love fest to the red carpet and beyond. Now, it was the Bronx's turn to get a look at the Hollywood power couple ... and they weren't shy.
Eyewitnesses spotted Ben and Jen touring the latter's birthplace borough, swinging by a place called Lit Bar in what we're told appeared to be a small biz tour -- with J Lo popping in to show love. BA was tagging along ... and apparently needed a smoke break between stops.
Check out this video TMZ obtained of Benny puffing on a cigarette and waving to fans who noticed him. He inhaled quickly, because he was back inside in no time -- but the cat was outta the bag ... because when they exited ... there was a swarm of people with phones out.