Spotify users who updated their mobile app this week saw something new and unexpected: a new icon on their phones that’s a shimmering green 3D disco ball. Spotify has been coy about what the new icon means, responding from its official main account on X to a post about the new logo: “isn’t she lovely? 💚” A Spotify rep confirmed to Variety that the disco ball is for the audio streamer’s celebration of the 20th anniversary of its founding. Presumably the Spotify disco-ball icon is temporary, but the company spokesman wouldn’t confirm that. As part of congratulating itself on its first 20 years, the streamer on Tuesday launched “Spotify 20: Your Party of the Year(s).” It’s a mobile-only in-app experience that provides look back at an individual user’s music listening history — including the total number of unique songs you’ve listened to, the first-ever song you played, and your all-time most-streamed artist.…