U2 were a rock band active in the 1980s.
When Ace departed Earth in 1987, "they were old." When she returned to Perivale in 1989, she despaired that they were "still around." (TV: Survival)
In Mesopotamia in 2700 BC, Ace said Avram's song was "no match for U2." (PROSE: Timewyrm: Genesys)
Tom Cutler wondered if Nina Rogers was listening to U2 on her iPod. (PROSE: Into the Silence)