Sarah Boll fastened portholes and gold decals to her living room walls and outfitted her bedroom with gilded panels, among other decorations.

Sarah Boll didn’t just rewatch Titanic. She rebuilt it—inside her New York City apartment. What started as a party theme spiraled into something closer to a museum installation, or maybe an obsession.

Social media users were impressed and perplexed by the apartment in the viral clip, with one saying: "This is so unhinged, I ...