"Since the musical opened on Broadway last year, an instrumental version of the classic 1960s song was played as patrons left the theatre. Now, beginning with the performance on Friday, October 2nd, the entire company will perform 'I'm a Believer,'" according to a Sept. 30 press announcement.

Composed by Diamond and recorded by The Monkees in 1966, the original single of "I'm a Believer" hit the number one spot on the U.S. Billboard Hot 100 chart on Dec. 31, 1966, and remained there for seven weeks, becoming the biggest-selling record for all of 1967.

Shrek, which plays the Broadway Theatre, will celebrate its one-year anniversary Nov. 8. A "SHREKtoberfest," a month-long festival of events leading up to that date, will feature discounted tickets, talkbacks with cast members, giveaways and more; visit www.shrektoberfest.com.

Shrek stars Tony Award nominee Brian d'Arcy James as Shrek, Tony Award winner Sutton Foster as Princess Fiona, Tony Award nominee Christopher Sieber as Lord Farquaad, Tony Award nominee Daniel Breaker as Donkey and Robb Sapp as Pinocchio.

Shrek, according to a press statement, "is an entirely new musical based on the story and characters from William Steig's book 'Shrek!,' as well as the DreamWorks Animation film."

For more information visit www.shrekthemusical.com.