“We knew from the script that he lived in an older, not good apartment, but he had taken a small studio and done something wonderful with it,” said Gardner, who also is production designer for “Veep.”

Whatever, indeed. Charlie's apartment turns out to be more complex than Marnie could imagine. Conceived by production designer Laura Ballinger Gardner, submitted to series creator Lena Dunham for her approval and then built from scratch — all in just four days — the fictional 12-by-12 studio set in the Bedford-Stuyvesant neighborhood of Brooklyn is a character unto itself.

“It looks awesome in here,” Marnie says upon seeing the studio for the first time, even though they have been a couple since 2007. “It looks like a Target ad. It's perfect.”

Sorry, “Girls.” When it comes to home design, the latest breakout star of the HBO series belongs to one of the guys: the apartment of Marnie's wet-noodle of a boyfriend, Charlie.

Charlie's back story, she said, is that he had a low-level job in an architecture office at one point and has worked as a carpenter. Thus an old metal box spring has been installed as a funky pot and mug rack in the kitchenette, while the rest of the space plays out as an ode to the handmade, including vintage-inspired screen prints on wood (from Ocho Loco Press in San Francisco) and modern rock posters (by the artist Scrojo in San Diego).

But it's Gardner's Mondrian-inspired birch plywood furniture that prompted fans to pause the DVR for a closer look. Her team built Charlie's wall storage unit, had it pigmented to achieve Mondrian-esque color blocks, and filled it with guitars and what seems like an impressive vinyl collection — rented by the foot from a prop house, actually. (Much credit, Gardner said, goes to set decorator Rich Devine, whose finds include vintage sewing machine lights turned into bedside sconces.)

Charlie's clothes are stored in more birch casework that doubles as steps to a raised lounging platform. The bed tucked under the raised platform was Dunham's idea, driven by a moment in the script when Charlie's declaration of “I love you” sends Marnie reeling in revulsion.

“It made for very funny measuring in the art department,” said Gardner, who added that crew members had to simulate certain intimate positions in bed to ensure Marnie would slam her head on the upper platform at just the right moment in the heavy breathing.

Charlie's apartment isn't the only “Girls” set that has fans a-Twitter. So while some viewers instantly hit social media to talk about the latest jaw-dropper (Did we really just witness that harrowing, hilarious full-frontal scene with Hannah's parents in the shower?), others inquire about paint colors and email Gardner about where her team bought furniture in Shoshanna's apartment.

To satisfy the curiosity about the show's residential sets, Gardner now Tweets (@lauraballinger) the names of artisans whose work she uses in the show, including an Etsy crafter who cross-stitches pillows with profane expressions.

And though much of fan love comes from people who wish they owned the looks, one of Gardner's personal favorites is the dump of an apartment belonging to Adam, the shiftless, perpetually shirtless boyfriend of lead character Hannah (Dunham).

“I love how gross it really is,“ Gardner says, laughing. “The palette bed, the dirty rug ...”

-- Craig Nakano

Marnie soon finds Charlie's bed alcove to be suffocating in more than one way. Production designer Laura Ballinger Gardner said the false wall behind the bed can be pulled away so camera crews can shoot key angles. The sconces were a vintage find; most of the lighting in the apartment is from Ikea.

"Those toolboxes by the front door are quite expensive," Gardner said. They are Gerstner & Sons pieces, "very beautiful, American-made wood toolboxes. People don’t want to carry them around anymore because they’re heavy, but we thought it’s something he would have." Charlie's layered rugs try to hide his cheap, contractor-grade linoleum floor.

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Rendering: Anne Allen Goetz / Laura Ballinger Design

Photos from Laura Ballinger Design