While Naomi Osaka fought through her U.S. Open quarterfinal in Queens on Wednesday evening, an artist named Kerin Rose Gold was at a gallery in Lower Manhattan, anxiously checking the score on her phone.

Ms. Osaka unleashed a series of exacting groundstrokes to win the first set, then stalled to a tie in the second. Once the tennis star had climbed to a 3-1 lead in the deciding tiebreak, Ms. Gold excused herself and raced back to her studio.

She had what might be called a bedazzling emergency. She needed to encrust a five-inch elf figurine with “a few thousand” crystals — and she had less than 24 hours to do it.

Ms. Gold, 42, is the artist behind the sparkling Labubu-style dolls that Ms. Osaka has carried with her to each match of the tournament so far. Each one is embellished by hand and named to wink at a tennis colossus: Billie Jean Bling. Arthur Flashe. Althea Glitterson.

Labubus — paunchy little creatures with apple cheeks and vaguely menacing grins — have swept through pop culture in recent months. Ms. Osaka has unveiled each of hers in a post-match flourish: After her win against Karolína Muchová on Wednesday, she showed off a hot-pink figurine complete with a mini tennis racket.

“This is Andre Swagassi,” she said with a giggle during a televised interview. “He’s very unique.”