The group consists of members Caro, Alex, and Charles,[1] who also operate as solo acts under the names caro♡, DJ Kit (formerly City Links), and Ultralove, respectively.
Alex described the defining characteristics of their music as a "minimalistic shoegaze loop with over-processed vocals on top of it.
[3] Often featured in Planet 1999's visuals is a mascot named Zippy which was designed by artist Leomi Sadler.
They met after Caro attended a psychedelic rock concert in Paris and found a flyer from Charles and Alex saying they were looking for a singer.
[2] In November 2019, they performed at fellow PC Music artist Hannah Diamond's concert in Paris during The Invisible Tour.
[11] The group has named artists Cocteau Twins, Hannah Diamond, Frank Ocean, Croatian Amor, and Uli K as some of the biggest inspirations for the project.
[15] It was released alongside a Bandcamp exclusive bonus demo album titled the lost logic files vol.1.
[21][22] It will again be released alongside a Bandcamp exclusive bonus demo album titled the lost logic files vol.2.