Wally Kestler is the first love interest of Julie Flinders in the LDS musical Saturday's Warrior. He is a Mormon missionary who is sent to Los Angeles on a mission to preach the gospel for two years.
Wally makes Julie, as his fiancée, promise (though it takes a musical number from her to him and three other women to three other missionaries ["Will I Wait For You?"]) that she will wait for him before he leaves for his mission.
Julie has been writing him letters and receiving letters from him, only (as one of her siblings, Benjy, puts it) blubbering whether she gets a letter from him or she writes one to him. The engagement lasts only two months, for no baptisms are done, and he isn't working hard enough. He has had two companions: a lazy, unnamed one, who is supposedly put in the hospital, and one named Harold Greene, with whom Wally was destined to preach the gospel in the first place. Because of the third letter (about Elder Greene doing as he says without complaining), Julie sends him a "Dear John" letter, much to his dismay and decision never to trust a girl again. Ironically, he breaks down over losing Julie.
Eventually, near the end, Wally and Harold preach to Tod Richards who decides to be baptized.