Hollywood actress and Environmentalist Cameron Diaz has made a surprise visit to a Stanford University classroom to help with a lecture on environmentally friendly designs.

The actress, known for her reality-travel show "Trippin" to help promote ecological awareness and who also drives a hybrid car, served as a sidekick for friend and renowned environmental architect William McDonough, a consulting professor at Stanford.

"He's very charismatic, captivating," Diaz says of McDonough, who Time magazine once called "Hero for the Planet." "Bill is one of those people who is thinking big, but is also producing."

Students later lined up to pose for pictures with the bubbly actress.

Diaz is best known for her roles in the "Charlie's Angels" films and has recently been seen on the big screen in "In Her Shoes", alongside Aussie actress Toni Collette.