The demonstrators were part of an anonymous group formed on the Internet. They believe the church suppresses free speech by suing and threatening anyone who opposes them.
"We believe in total freedom of belief. We have nothing against the people of Scientology, however the Church of Scientology has committed crimes. They're vehemently anti-opposition. Anyone who opposes them, must go down," said one protestor.
Disguised with fake beards, face paint, scarves and bandanas, protesters said they hid their identity for fear they would be tracked down and harassed by Scientology.
Organizers - who held rallies in London, Paris, New York and other cities around the world - chose Sunday's date because it would have been Lisa McPherson's 49th birthday. A 36-year-old Scientologist, McPherson died in 1995 while in the care of church staffers.
Anonymous will next be seen in action on March 15, celebrating L. Ron Hubbard's birthday. March 13 is Hubbard's actual birthday - a day of celebration for Scientologists around the world.