When Cory wishes that Feeny would get better, he asks God to send a sign, and he looks out to see Feeny's vintage duck fall over. Earlier in the episode, we see Feeny put it up and it is lined up with the door. When it falls, it is on the left side of the lawn.
When Corey was telling the substitute teacher that Beowolf and Geography are useless, Boom mic is visible on the top of the frame.