Jennifer Lopez -- Jenny PHOTOBOMBED Down the Block

Jennifer Lopez -- who knows a thing or 2 about bombs -- looked as pained as someone who sat through more than 10 minutes of "Gigli" when some random dude photobombed her Tuesday on the streets of Bev Hills.

JLo was hoofing it with boy-friend Casper Smart when Mr. Jazzy Hands auditioned for a back-up role.

Pretty sneaky maneuver -- the kind of sneakiness that would even impress Mr. Deeds' right hand man.