In fact, both of these balls are called “The Green Inaugural Ball,” which could certainly lead to confusion for guests invited to both. One ball will be held by Al Gore and the other by PETA. From the Baltimore Sun:

People for the Ethical Treatment of Animals plans to give away fur coats to the homeless while offering hot soy-milk cocoa in cups that read: “Thank You for Not Wearing Fur!”

Many of the other balls are encouraging attendees to carpool, will serve organic foods, and are using energy-efficient lighting.