Collins, best known to TV audiences for his role as Rev. Eric Camden in the WB/CW series "Seventh Heaven," assumes the role of King Arthur. Lachey, who was the second season champion on ABC's "Dancing With The Stars," steps into the role of Patsy, Arthur's trusted manservant.

Collins and Lachey join a cast that currently features Marin Mazzie, Wally Dunn, Tom Deckman, Rick Holmes, Bradley Dean and Robert Petkoff.

Spamalot features a book and lyrics by Eric Idle, music by John Du Prez and Eric Idle, direction by Mike Nichols, choreography by Casey Nicholaw and is based on the screenplay of "Monty Python and the Holy Grail" by Monty Python creators Graham Chapman, John Cleese, Terry Gilliam, Eric Idle, Terry Jones and Michael Palin.

The musical tells the tale of King Arthur and his Knights of the Round Table on their quest from God for the Holy Grail — with a short stop in the dazzling Spam-filled land of Camelot.

Spamalot earned the 2005 Tony Award for Best Musical and took home honors for direction (Mike Nichols) and one of its stars (Sara Ramirez).

Spamalot celebrated its third anniversary on Broadway March 18.

Stephen Collins has been seen on Broadway in Moonchildren; No Sex Please, We're British; The Ritz; Censored Scenes From King Kong; and The Loves of Anatol. Drew Lachey made his Broadway debut in Rent.

On Broadway Spamalot plays Tuesday-Friday at 8 PM, Saturday at 2 and 8 PM and Sunday at 2 and 7 PM.

For more information visit www.montypythonsspamalot.com.