The small snow creatures Elsa creates in Frozen Fever are called Snowgies.
Elsa accidentally produces the tiny snow-people whenever she sneezes during Anna's birthday celebration. She has caught a cold, and each sneeze magically creates more Snowgies, turning the carefully planned party into a chaotic parade of miniature troublemakers.
The Snowgies are connected to Elsa's ice powers, much as Olaf and Marshmallow are magical beings shaped from snow and ice. Unlike Olaf, however, they are tiny, numerous, and largely focused on mischief. They help disrupt the decorations before eventually joining the birthday gathering.
By the end of the short, Olaf, Kristoff, and Sven escort the Snowgies to Elsa's former ice palace, where Marshmallow lives. Viewers sometimes confuse them with Marshmallow, the large snow giant guarding Elsa's palace, but Marshmallow is a separate character. The Snowgies later appear in Frozen II’s post-credits scene.