Even the greatest names in entertainment had to start out somewhere. Jack Nicholson and Brad Pitt were once nothing more than lead actors in school plays, for example. Here's another legendary name at the start of his career - it's Robin Williams in Central Park.
Williams possessed an incredible ability to make people laugh, and demonstrated it throughout his life. We assume he was even able to find a way to make a mime act funny, which is what he was attempting here in 1974.