Winsor Z. McCay bets another cartoonist that he can animate a dinosaur. So he draws a big friendly herbivore called Gertie. Then he get into his own picture. Gertie walks through the picture, eats a tree, meets her creator, and takes him carefully on her back for a ride.

Cartoonist Winsor McCay agrees to create a large set of drawings that will be photographed and made into a motion picture. The job requires plenty of drawing supplies, and the cartoonist must also overcome some mishaps caused by an assistant. Finally, the work is done, and everyone can see the resulting animated picture.