Police say one woman, Coura Valazquez, went to municipal court with two friends, Brittany Medak and Leokham Yothsombath, on Monday afternoon to pay a fine. The show began as they headed to the parking lot.
Police say they exposed themselves as one of the women filmed the moves.
The Oregonian reports one lifted her skirt and urinated between two cars. They also were accused of bringing drugs to the Courthouse.
Police stopped their car a few blocks away as they were driving away and arrested the two 20-year-old Vancouver, Wash., women and 22-year-old Portland woman.
The three had marijuana, cocaine, methamphetamine and prescription drugs on them, police said.