During one of the conversation segments in the documentary Lars von Trier and Jørgen Leth agree that Leth will receive full credit for the fifth and final Obstruction entitled "The Perfect Human: Avedøre, Denmark" despite not directing it, and that Trier will receive none, although he will direct it. This, apparently, is within the rules of the game played out by the two directors during the documentary, and serves as an inside joke.
The song played during The Perfect Human: Havana is "Planting the Seed" by David Holmes, which was also used in Ocean's 11 and appears on that movie's soundtrack.