No reason was given for the cast change. Directed by John Tartaglia and choreographed by Vince Pesce, the limited engagement will continue through June 30.

The cast will also feature the previously reported Julia Murney as Princess Fiona, Rob McClure as Lord Farquaad, Michael James Scott as Donkey and Natalie Venetia Belcon as Dragon.

Wallem is a SAG Award-nominated actor best known as Thor on the Emmy-winning Showtime series "Nurse Jackie," now in its fifth season. He began his career as a stage actor and After Dark Award-winning cabaret singer in Chicago. New York credits include Hazel in the Encores! production of Rodgers and Hammerstein’s Pipe Dream at New York City Center and teaming with Edie Falco for a sold-out run of the original cabaret The Other Steve and Edie. National tours include Forever Plaid, Into the Woods and Scrooge starring Richard Chamberlin. He will be making his professional opera debut this September in Anna Nicole for New York City Opera.

Based on the classic film, Shrek The Musical has a book by David Lindsay-Abaire and music by Jeanine Tesori.

The Muny production will feature scenic design by Steve and Sam Gilliam, sound design by Jason Krueger, lighting design by Nathan Scheuer and costume design by Andrea Lauer. Greg Anthony serves as the musical director, and the production stage manager is Michael Clarkston.

For more information, call (314) 361-1900 or visit www.muny.org.