Green Day surprised fans at San Diego Comic-Con by performing their 1994 hit 'Basket Case' from atop an ice cream truck, promoting their upcoming coming-of-age film "Nimrods". Billie Joe Armstrong began the impromptu set alone on the roof of a truck branded with the film's title, before bandmates Mike Dirnt and Tré Cool joined him, later handing out ice creams to the crowd from inside the vehicle. The stunt, staged in Gallagher Square outside Petco Park on 24 July, generated a wave of enthusiastic reaction online.

The film, directed by Lee Kirk and developed with the band, follows three friends who mistakenly believe their band has scored a support slot with Green Day, in a road-trip story inspired by the band's own early years living out of a tour van before 1994's "Dookie". It stars Mason Thames, Jenna Fischer and others, and opens in UK cinemas on 11 August and US cinemas on 14 August. Green Day are also releasing an accompanying 22-track soundtrack on 31 July, featuring a new song, "I'm Never Gonna R.I.P.", and previously unreleased live recordings.