Continuity mistake: The father was known as Clifford in the beginning but the name was changed to Heathcliff (you can see this on the nameplate for his office).
Continuity mistake: After Theo gives up an extra $100 for clothes, he is holding $300 left in his hand. However when the camera switches back to Cliff, who asks how much is left, it switches back to Theo, who is only holding $200 left.
Chosen answer: That is the song "Open the Door Richard."