His strips Little Nemo and Dreams of a Rarebit Fiend were both set in the dreams of their characters and featured fantasy art that attempted to capture the look and feel of dreams. McCay's cartoons were never overwhelmingly popular, but always had a strong following because of his expressive graphic style. Newspaper pages were physically much larger in that time and McCay usually had a half a page to work with. For fantasy art in comics, his only rival was Lyonel Feininger, who went on to have a career in the fine arts after his comics days were over.
McCay also created a number of animated short films, in which every single frame of each cartoon (with each film requiring thousands of frames) was hand-drawn by McCay himself. McCay went on vaudeville tours with his films. He presented lectures and did drawings; then he interacted with his animated films, performing such tricks holding his hand out to "pet" his animated creations.
Laid out with exquisite detail in a manner that would only be matched during the heights of Walt Disney's cartoons of the 1930s, the star of McCay's groundbreaking animated film Gertie the Dinosaur is classified by film and animation historians as the first cartoon character created especially for film to display a unique, realistic "personality." In the film, Gertie causes trouble and cries when she is scolded, and finally she gives McCay himself a ride on her back as he steps into the movie picture.
In addition to a series of cartoons based on his popular "rarebit" gags, McCay also created The Sinking of the Lusitania, a realistic depiction of the attack on the martime ship. The cartoon contained a message that was blatant propaganda, meant to inspire America into joining World War I.