With his partner Lowell Ganz, Mandel has written some of the most popular comedies of the last decade. Their credits include a number of films produced by Brian Grazer, Ron Howard and their Imagine Films Entertainment, including Ron Howard's "Night Shift" (1982), the Oscar-nominated "Splash" (1984), "Gung Ho" (1986) and "Parenthood" (1989).Mandel and Ganz met in a Hollywood comedy club while the former was working as a joke writer and the latter was working as a staff writer on "The Odd Couple.” The two transplanted writers from New York who idolized Billy Wilder became fast friends. A day