New York, New York - After Billie Eilish stunned on the 2023 Met Gala red carpet, she gave fans an inside look at the annual fashion event with a sneaky selfie!

The 21-year-old went full gothic glamour for her ensemble this year, which was a custom Simone Rocha number.

Once she headed up the famous Met steps and inside the gala, Eilish broke one of Anna Wintour's rules for the evening alongside some star-studded company!

In a selfie shared to her Instagram story on Tuesday, the Ocean Eyes singer posed alongside Halle Bailey, Maya Hawke, and Elle Fanning in front of a bathroom mirror.

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The mirror featured several signs warning guests not to smoke, and Eilish played up the notices with two added "no smoking" emojis above the photo.

Though Wintour reportedly sent a notice to all Met Gala attendees in 2015 that phones could not be used for photos once inside the event, a number of celebrity guests have broken the rule in the years since.

Perhaps the most famous breaking of the rule came from Kylie Jenner, who took a bathroom selfie in 2017 that included an impressive number of stars, including her sisters Kim and Kendall, A$AP Rocky, Paris Jackson, Frank Ocean, Lily Aldridge, Sean "Diddy" Combs, and more.

At this year's gala, Lil Nas X repeatedly broke the rule as he shared selfies with a number of fellow attendees inside the museum.

Eilish even broke the rule again with the Old Town Road rapper with another selfie he shared on Twitter during the event.