"I think the last record was very much a sort of U2 fan base record. I don't think we made a hell of a lot of new fans on that record. And with this album, I believe we can."
- The Edge on Songs of Innocence, 2014
The lyric "3:33 when the numbers fell off the clock face" from Unknown Caller is a reference to the Bible verse Jeremiah 33:3. Bono refers to it as "God's phone number".