Buena Vista Street - Mortimer's Market: Instead of the pretentious sounding Mortimer Mouse, Lillian convinced Walt Disney to go with the more jovial name Mickey. After debuting in 1928 Mickey's popularity grew. The name Mortimer bounced around in Walt Disney's head until 1936. A tall, thin Mortimer Mouse first appeared as Mickey's nemesis in the cartoon short Mickey's Rival (June, 20, 1936).