The musician, Callum McMorran, covered the band's 1997 classic "Good Riddance (Time of Your Life)" A singer in Liverpool got an unexpected visit during his set. On Tuesday, Jan. 7, Billie Joe Armstrong watched Callum McMorran perform Green Day's hit "Good Riddance (Time of Your Life)" at Cavern Club in Liverpool.

Billie Joe Armstrong was visiting some of Liverpool's iconic music locations, and happened upon a local musician playing one of his own songs

Resident performer Callum McMorran thought it was just another Tuesday – turns out Billie Joe Armstrong had been watching his performance

That's exactly what happened to Callum McMorran on Tuesday night (January 7) when he covered Green Day's "Good Riddance (Time of Your Life)" at Liverpool's Cavern Club and saw Billie Joe Armstrong in the crowd.