Answer: Some of them don't! Matthew Broderick's difficulty remembering lines during performances of Kenneth Lonergan's new play The Starry Messenger has, ahem, prompted a long article in the Times on the history and ethics of learning lines. The takeaway is that some actors, including the great Angela Lansbury, use earpieces to stay on cue.

Line prompters were common at one time, and Lansbury says, "In the early days of theater, there was a ‘prompt corner’ with a person ready to throw the line to any actor. In the electronic age, some 80-year-old performers wear earpieces. And all of us lose ourselves in a play at moments. Laurence Olivier did at the height of his career. This is part of theater." Hugh Jackman, on Broadway now in a play with Daniel Craig, quips, "I hope we won’t have to use cue cards."

Now Actors Equity is investigating the firing of 49-year-old actor Matt Mulhern, who hid some lines inside his hat to stay on cue during Horton Foote’s nine hour play cycle. Mulhern tells the Times he was "emotionally devastated" by the dismissal, the first of his 27-year career. But he also acknowledged he had “ruffled feathers” during rehearsals for other reasons.

As for Broderick, theater nerds have been calling for his head on sites like talkinbroadway.com, where one user wrote, "For God's sake, they are charging good money for this, and it is indeed unconscionable to use these as rehearsals. I only hope they do cancel this week of performances because I, too, have a ticket, and I don't want to endure this either." A source tells the Daily News, "It was an overall mess. He kept apologizing under his breath after he forgot a line, and everyone in the audience started to feel awkward."