Hunter Foster, who created the role of Bobby Strong, leaves March 16 to be replaced March 18 by Charlie Pollock.

Kayden and the Tony-nommed Thompson replace Megan Lawrence and Anastasia Barzeee, respectively. Foster is off to rehearse the role of Seymour in the Broadway-bound Little Shop of Horrors. Pollock was a standby for Off-Broadway's tick, tick...BOOM! and makes his Broadway debut as the young revolutionary in Urinetown.

Thompson took some time off from the satiric Urinetown to play the world premiere of Little Fish, the Michael John LaChiusa musical at Second Stage. Thompson was nominated for a 2002 Tony Award for Best Actress in a Musical for her performance as the ditzy daughter of an evil magnate who controls the water supply in the futuristic Urinetown.

Kayden received the 2001 Clarence Derwent Award, the Outer Critics Circle Award and nominations for Tony, Lucille Lortel and Drama Desk Awards for her performance as Little Sally, the pig-tailed girl-woman who helps explain the plot of Urinetown.

Urinetown, the musical, plays The Henry Miller, 124 W. 43rd Street, between Sixth Avenue and Broadway. *

Urinetown has book and lyrics by Greg Kotis, music and lyrics by Mark Hollmann and is directed by John Rando (all three took home 2002 Tonys for their work). Musical staging is by John Carrafa. The writers are currently working on a screenplay for the darkly comic show.

The Urinetown cast also includes Victoria Clark as Penelope Pennywise, John Cullum as Caldwell B. Cladwell and Jeff McCarthy as Officer Lockstock, with David Beach, Jennifer Cody, Rachel Coloff, Rick Crom, John Deyle, Joanna Glushak, Victor W. Hawks, Ken Jennings, Stacie Morgain Lewis, Daniel Marcus, Peter Reardon, Don Richard, Lawrence Street and Kay Walbye.

Performances play 7 PM Tuesday, 8 PM Wednesday Saturday, 2 PM Wednesday and Saturday, 3 PM Sunday.

Tickets range $35-$95. Call (212) 239-6200 for information.