Long Strange Trip may be hogging the spotlight this year, but it’s not the first film the Grateful Dead appeared in. That would be Petulia from 1967, which–disappointingly–is not the Petulia Clark story.
Richard Lester, the guy who directed the Beatles’ movies, did this one; it’s about George C. Scott beating Julie Christie or something. He also takes some time to look appalled by the young people, and order pressed duck. (That’s what the waiter’s doing at the end of the clip. “Pressed duck” is not a euphemism: they put the whole bird in there and squeeze it until it’s yummy.)