Near the end of a remarkably high-energy show, the singer sat down on a small outcropping of the stage to be as close to the audience as possible to sing "What Was I Made For," her gorgeous lament from last year's "Barbie" soundtrack.
But three words into the song, Eilish was interrupted by a flying object; a fan, perhaps mistaking this for a Taylor Swift concert, threw a bracelet to her. The bracelet seemed to hit the singer on the chest, startling her in such a way that it initially seemed as though she was hit in the face. The incident made her briefly stop the song.
It wasn't the first time fans threw things on the stage that evening; there was at least one bra and possibly a teddy bear or other stuffed animal. But it was the only gift that made physical contact.
Eilish recovered quickly and delivered a moving rendition of the tune, which won an Oscar for Best Original Song and a Grammy for Song of the Year.
But just a couple songs later, as Eilish sang the song "Happier Than Ever," she sang the line "You make me hate this city" with particular fervor.
The bracelet incident was a vibe-killer in an evening that was mostly a lovefest between Eilish and the audience, who screamed endlessly for the young star.
See video of the incident below: