In my serach for more info about Elsie and the fair, I can across the following:
"Paul Charles Castellanos Jr. died on Apr. 3, 2000, at Muhlenberg Regional Medical Center in Plainfield, N.J. He was 71.
After graduation from Princeton, class of 1950, Paul served in the navy for four years and then joined Borden, Inc., in marketing. He was Elsie the Cow's road manager for the next 16 years, including the 1964-65 New York World's Fair. Paul, a member of MENSA, also worked for Public Relations Society of America and was self-employed for 10 years.
Paul was a widower and is survived by three daughters, Karen C. Badalaty, Sandra Owen, and Diane C. Joest, and eight grandchildren."