McDonel is a Kings High School graduate who worked at the park from 1981 to 1986 in food service.
Kings Island spokesman Don Helbig said McDonel was “totally surprised” when he reached the ride platform and was informed that he would take the one millionth ride on the popular attraction, billed as the park's "fastest, tallest, meanest" roller coaster.
McDonel received a Diamondback gift package that included a tote bag, T-shirt, cap, puzzle, poster, playing cards and a large sign proclaiming him Diamondback’s one millionth rider.
The $22 million roller coaster is on course to be the most popular debut for a ride in more than 20 years, Helbig said.
The last Kings Island coaster to attract such a following during its debut was Vortex, which opened in 1987 and amassed 2,183,642 rides that season.