I feel like Billie is HEAVILY inspired by MCR and Frank Iero.
Examples:

Stomachaches = Album by Frank Iero
Bellyache = Song by Billie Eilish

"I'm Not Okay" = Lyrics/Song by MCR
"I'm not okay" = Lyrics from the song 'Listen Before I Go' by Billie Eilish

"I'm Okay" = Lyrics from the song 'I'm Not Okay' by MCR
"I'm Okay" = Lyrics from 'You Should See Me In A Crown' by Billie Eilish

Six Feet Down Under = Song by Frank Iero
Six Feet Under = Song by Billie Eilish

Don't you think so too?