Alfred the Gorilla
Alfred died on 10 March 1948. The press at the time speculated that ‘his pet hate got him in the end’, linking Alfred's dislike of aeroplanes with the passage of one over the zoo shortly before his death. The actual cause of his demise was tuberculosis which he contracted a year before and despite his keepers best efforts, he had been unable to recover. His death was mourned by many of the regular visitors to the zoo, some of whom were even inspired to compose poems in his honour.
Alfred Pennyworth
Ironically, Alfred's loyalty would lead him to become a member of Batman's rogue's gallery. While pushing Batman and Robin out of the way of a falling boulder, Alfred was seemingly killed in "Detective" #328 (June 1964). It was revealed in "Detective" #356 (October 1966) that he had been revived by a scientist named Brandon Crawford. His attempt at regeneration resulted in a dramatic change: Alfred awoke from his apparent death with pasty white skin with circular markings, superhuman powers, including telekinesis, and a desire to destroy Batman and Robin. Calling himself The Outsider, he indirectly battled the Dynamic Duo on a number of occasions, using others as his puppets—the Grasshopper Gang in "Detective" #334, Zatanna in "Detective" #336, and even the Batmobile itself in "Detective" #340—and generally only appeared as a mocking voice over the radio. He did not physically appear in the comics until "Detective" #356, when he is bathed again in the rays of the regeneration machine during a struggle with Batman, and returns to normal, with no memory of his time as a supervillain. His time as the Outsider is collected in "Showcase Presents: Batman" Volumes 1 and 2.