When the Simpson family are at the dinner table and Homer puts his feet up, his strawberry wine can be seen hanging around his neck. When he can be seen in the shot with Marge's legs, the wine has disappeared. It reappears again seconds later when Marge takes it off of him.
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.
In the flashback to Woodstock which took place in August 1969, grandpa calls for Sha Na Na to perform and holds up a sign that reads "Bowzer for president". Bowzer did not join Sha Na Na until 1970.