Wikipedia screwed up. Alda was in the reserves AFTER he graduated from Fordham University in 1956, well after the Korean war.
http://www.military.com/Careers/Content1?file=trans_alan_alda.htm&area=Content
Alda joined the Army Reserve after graduating from Fordham. He completed the minimum six-month tour of duty as a gunnery officer during the Korean War.
http://www.museum.tv/archives/etv/A/htmlA/aldaalan/aldaalan.htm
Graduated from Fordham University, Bronx, New York, 1956
so Alda WAS in reserves after college but NOT officer in Korea other than in MASH!