The end credits for Mr Burns' recruiting movie say, "An Alan Smithee film." Alan Smithee is a fictitious name reserved (until the year 2000) by the Directors' Guild of America for movies which are so bad the actual director wants to disclaim all responsibility.
When Grandpa Simpson tells Homer about them attending Woodstock, he has a flashback of the concert. Jimi Hendrix is on the stage playing The Star Spangled Banner, and Grandpa is booing and calling for Sha Na Na to play. Sha Na Na already performed, from 7:30 to 8:00 AM on Monday August 18, 1969. Jimi Hendrix was the following act, and he closed the show, performing from 09:00 to 11:10 AM. The Star Spangled Banner was the 13th of 16 songs that he performed.