Casper the friendly . . . peep show patron?

Jennifer Lopez's main squeeze, Casper Smart, was photographed entering a 24-hour Peep Show in NYC Monday -- just one day before his girlfriend Lopez's 43rd birthday.

In the photos, Smart, 25, makes a phone call before heading in to the entrance just underneath the Peep Show's neon sign. (The Daily Mail points out Smart was seen adjusting his pants on his way out.)

PHOTOS: Jennifer and Casper's whirlwind romance

Of course, Smart may have just been making a pit stop on his way to get Lopez an extra special birthday gift at the Adult Toy Store next door -- and Smart was by his girlfriend's side for a romantic night out in NYC Monday evening.

Though they've only been dating since fall of 2011, things have heated up quickly for the former American Idol host and her backup dancer.

PHOTOS: Jennifer's romantic history

"She's telling friends she wants to marry Casper," one confidante told Us Weekly this spring. "She's certain she wants to be with Casper forever."

This article originally appeared on Casper Smart Hits NYC Peep Show One Day Before Jennifer Lopez's Birthday