In the scene where Danny's mother is talking on the phone with his father, the television in the background is showing news footage of President Nixon leaving the White House after resigning from office. In this scene, "The Partridge Family" was still in production. Nixon left office in August 1974. The final episode of "The Partridge Family" aired in March 1974.
When Danny's family watches the first episode of the Partridge Family on TV, it opens with the theme song "Come On Get Happy." For the first season of the Partridge Family, the theme song was "When We're Singin'", not "Come On Get Happy."