SAN DIEGO, July 30 -- Nobody who was in Gallagher Square outside Petco Park on the afternoon of July 25 needed a trailer.

Billie Joe Armstrong was already up there, acoustic guitar in hand, perched on the roof of a Mister Freezie's ice cream truck wrapped in the title of his new film, playing "Basket Case" to several thousand Comic-Con attendees who had shown up for a stunt they knew almost nothing about. Mike Dirnt and Tre Cool eventually materialized behind him, and then the whole band climbed inside the truck and started throwing T-shirts, cassette tapes, and frozen treats into the crowd, according to NBC 7 San Diego.

This is either the most on-brand marketing campaign in recent Hollywood memory or the most elaborate piece of perform...