The Charlie's Angels star's appearance was filmed for the MTV series Stand In, where celebrities such as Marilyn Manson, Melissa Etheridge and Kanye West have appeared as guest lecturers at colleges across America.
Earlier last week, Madonna surprised students at New York's Hunter College when she turned up to take a film class.
Diaz, who is a champion of environmental causes, joined her friend and renowned environmental architect William McDonough who was taking the lecture.
Speaking about McDonough, Diaz says, "He's very charismatic, captivating. "Bill is one of those people who is thinking big, but is also producing.”
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