The omnivorous Shakespeare Geek usually beats me to the punch in relaying information about forthcoming Shakespeare films and cultural references to Shakespeare—which is why you should all follow his blog as well as mine—and this is no exception. In fact, Shakespeare Geek's blog called my attention to this Shakespeare reference in Friends. His post, written in 2008, mentions a brief Shakespeare joke in the show; however, his post doesn't provide the context or a nifty video clip. I felt that it was up to me to do so.
In this clip, Joey is mad at an actress who is treating him as an inferior because of her training in drama. Searching for a way to explain how she thinks she's better than anyone else, Joey ends his sentence with a cliché that doesn't quite jive with the beginning of his sentence:
Chandler is quick to jump on the incongruity and to imagine a speculative actress who is actually named Sliced Bread (the caption on the image above should have capitalized "Bread" to stay with the joke)—one who made herself memorable as great by playing the role of Lady Macbeth. Once again, Shakespeare demonstrates his usefulness as a marker of cultural greatness—as does Shakespeare Geek.
Links: The Episode at IMDB.