Wolfgang Van Halen made an unexpected appearance during the Foo Fighters’ headlining set at Welcome to Rockville on May 11, performing parts of the classic Van Halen tunes “Eruption” and “Hot for Teacher.” The surprise came roughly halfway through the Foos’ set, when Dave Grohl typically cedes the spotlight to his bandmates for a medley of cover songs and extended solos. On this occasion, Grohl complained about the usual routine. “You know who never gets a fucking solo? Me. I never get to fucking solo,” the frontman bemoaned. “Alright, ready motherfuckers? Here we go!” Grohl then declared as h…