In 1928, Walt Disney produced a cartoon starring the little mouse soon to be known as Mickey Mouse. At that time the mouse was not known as Mickey Mouse, but by what two-word name?

While the name "Steamboat Willie" is inextricably linked with the debut of the world's most famous mouse, the character himself was not known by that name. The trivia answer points to the title of his landmark 1928 cartoon, a production that marked his first appearance to the general public. This short film was a sensation, not only for its charming new character but also for being one of the first cartoons to feature a synchronized soundtrack, with music and sound effects that matched the on-screen action.

Before the little mouse ever graced the silver screen, Walt Disney had a different name in mind for his creation: Mortimer Mouse. However, at the suggestion of his wife, Lillian, who found the name "Mortimer" to be too pompous, he opted for the friendlier-sounding "Mickey." By the time of his first film screenings in 1928, the character was officially known as Mickey Mouse. In fact, two silent cartoons, "Plane Crazy" and "The Gallopin' Gaucho," were produced before "Steamboat Willie" and also starred the character under the name Mickey Mouse, though they failed to find a distributor initially.

Therefore, the name "Steamboat Willie" is the correct answer because it is the two-word title of the cartoon in which the character, who was already named Mickey Mouse, made his public debut. The film's plot follows Mickey as a deckhand on a river steamboat, getting into mischief and making music with the objects and animals on board. The immediate popularity of "Steamboat Willie" launched the Disney empire and cemented Mickey Mouse as an international icon.