Jeffrey Charles William Michael `` Jeff '' Conaway ( October 5 , 1950 -- May 27 , 2011 ) was an American actor known for his role of Kenickie in the movie `` Grease '' and two US television series `` Taxi '' and `` Babylon 5 '' .
Jeffrey Charles William Michael `` Jeff '' Conaway ( October 5 , 1950 -- May 27 , 2011 ) was an American actor . He appeared in the movie `` Grease '' and the television series `` Taxi '' and `` Babylon 5 '' .