Green Day surprised fans at San Diego Comic Con on July 24 with an unusual performance of “Basket Case” from the roof of an ice cream truck.

The band appeared at Gallagher Square outside Petco Park to promote its upcoming coming-of-age film, Nimrods. Frontman Billie Joe Armstrong first climbed onto the roof of a Mister Freezie’s truck, which had been decorated with the film’s title, to perform the 1994 Dookie hit. Bassist Mike Dirnt and drummer Tré Cool later joined Armstrong for the spontaneous outdoor set.

The performance turned the truck into a small stage as fans gathered around to watch the band play one of its biggest songs. Armstrong also threw ice creams, T-shirts and cassette tapes into the crowd before the three members climbed into the truck and helped hand out frozen treats.

Nimrods actors Mason Thames and Jenna Fischer attended the surprise event alongside writer and director Lee Kirk. The film is due for a limited release in United Kingdom cinemas on August 11 before arriving in U.S. theaters on August 14.

Developed by Kirk alongside Green Day, Nimrods follows three friends who travel from Kansas City to Los Angeles after mistakenly believing their band has been selected to open for Green Day on New Year’s Eve. The story draws inspiration from Green Day’s own early years, including the time the group spent touring in a van before its breakthrough with Dookie.

An accompanying Nimrods soundtrack will arrive July 31. It features 22 songs from across Green Day’s career, as well as music from The Paradox, Ultra Q, Mckenna Grace and Analog Dogs. The soundtrack will also include the new Green Day song “I’m Never Gonna R.I.P.” and four unreleased live recordings from a Los Angeles Palladium performance featured in the film. Green Day last released its studio album, Saviors, in January 2024.

Earlier this year, mxdwn reported on producer Linda Perry’s criticism of Green Day and Billie Joe Armstrong over her removed involvement with 21st Century Breakdown. The band now returns to celebrating its earlier history through Nimrods, a film inspired by the years surrounding its Dookie breakthrough.