Billie Eilish shocked and endeared Paramore fans when she jumped on stage last night to sing "All I Wanted" with the band at the Forum in Inglewood.

Fans were already excited when they heard the opening strains of the 2009 song from Brand New Eyes and had begun singing along with Hayley Williams.

After the first verse, Williams casually said, "please welcome our friend Billie Eilish," as you do, who walked out and began dancing to the climatic energy that comes with the build up.

Hayley in a sparkly short dress and go-go boots and Eilish rocking a long black shirt with matching shorts, black socks, black hi-top Chucks, and red striped tie, danced happily like the entire crowd at the sold out arena.

I think I'll pace my apartment a few times
And fall asleep on the couch

Haley took over for the longing chorus "All I wanted was youuuuuuu" which the audience was right there with her.

"All I Wanted" was released in 2009, a year after band was Grammy nominated as Best New Artist (which went to Amy Winehouse, naturally. No shame.) And, don't freak out, in 2009, Billie was 7.

The giddy smiles the two female singers exchanged during the song were adorable and so genuine. In 2022 after Eilish invited Williams on stage at Coachella for "Misery Business," the LA native was asked what her favorite Paramore song is, she said it was "All I Wanted."

What a beautiful way to see that all come full circle.

This morning Eilish, clearly still flying high from the experience, took to Instagram to express her love for Williams and happiness for being able to share that moment with her.

"UGHHDKSLDJSKFJKSKFUDJSKKFKDKDK dream come truEEEEEE," Eilish wrote on her IG post that featured clips from the moment and one older video of Eilish doing aerial dancing to "All I Wanted" back in the day.

"wish i could tell tiny me," Eilish wrote.

In reply Williams posted the pair's embrace on her IG story with the caption "love you sweet billie."

And then Williams' reposted young Billie aerial dancing to the song and wrote "will protect you at all costs".

Could anything be more heartwarming?

It was a night of mutual admiration as earlier in the night Williams joined Muna to the delight of both the audience and the young musicians.

Meanwhile backstage, Dave Grohl and bass legend Thundercat got to meet the Linda Lindas who were also on the bill.

Inglewood might be called "The City of Champions," but last night it was the City of Sweet Sweet Smiles.

Paramore has a few more U.S. dates - including another night, tonight, at the Forum - before they take a break and jet to Australia in November. Get your tickets on the Paramore site.