And So We Commence (1) - S8-E24
Plot hole: When Theo is complaining that his father is inviting too many people to his graduation, he says "I saw him in the backyard 5 minutes ago hosing down the beach chairs", but this couldn't have been possible because in fact, Cliff was upstairs right before that scene, and then went straight to the living room, so there's no possible way that Cliff could have been in the yard at the time Theo had said he was.
Plot hole: At the beginning of the episode, Theo, Vanessa and Rudy all act as if they forgot Clair's birthday. But Rudy already had a present for her mother's birthday, the pendant she ordered in the episode, "Cyranoise de Bergington".
Chosen answer: That is the song "Open the Door Richard."