Joey: I kind of had a dream. But I don't wanna talk about it.
Chandler: Whoa, whoa, whoa, whoa, whoa! What if Martin Luther King had said that?
This is a reference to Martin Luther King, an African American civil rights activist who is perhaps most famous for his "I Have a Dream" speech, given in front of the Lincoln Memorial during the 1963 March on Washington for Jobs and Freedom.