The name "Mickey Mouse" was often used in the films' title sequences to refer specifically to the character, but sometimes also to the series itself, as in "Walt Disney presents a Mickey Mouse".
The name "Mickey Mouse" was used in the films' title sequences to refer specifically to the character, and later as the series itself. "A Mickey Mouse" in this later sense was truncated from "a Mickey Mouse sound cartoon", as in "Walt Disney presents a Mickey Mouse".