Harold Hooper ran Hoopers Store
on Sesame Street
when he died
Big Bird always got his name wrong, most commonly calling him Mr. Looper. (Big Bird actually got his name right once, and only once, when Mr. Hooper broke his arm.)
Mr. Hooper was played by Will Lee.
(More at http://members.tripod.com/~hooperfan/index-2.html)