LOS ANGELES John C. Reilly remembered being enthralled watching ''Showtime'' basketball with Magic Johnson's no-look passes and Kareem Abdul-Jabbar's patented skyhook, but the actor never really knew the backstory behind the Los Angeles Lakers dynasty. Reilly quickly found out after stepping into his role as late Laker owner Jerry Buss in the HBO series ''Winning Time: The Rise of the Lakers Dynasty,'' which airs Sundays. ''That was the vehicle through which the entire (basketball) world was changed,'' said Reilly about the Lakers, which was bought by Buss in 1979.