It's not the first time Billie Eilish and Charli xcx celebrated birthdays together with the sounds of "Guess." In August 2024, Eilish was among the guests at Charli xcx's birthday party in Los ...

At the latter, the night is starting off strong with Billie Eilish joining Green Day for 21st Century Breakdown’s “Last Night On Earth.” Eilish walked onstage partway through the song.