The use of animations in behavioral research is limited by the technical complexity of creating realistic, moving three-dimensional stimuli. In collaboration with experts in animation and visualization, we have created anyFish, an open-source program for creating realistic animated stimuli representing the most widely used fish models in animal behavior. Researchers can create stimuli using data frequently collected by biologists, including digital recordings of behavioral sequences and geometric morphometrics. The modular structure of anyFish makes it straightforward to incorporate biological variation into a stimulus set. anyFish is free and open-source, without funds to provide technical support. The usefulness of the program, and prospects for future improvements and additional funding, depend on the enthusiastic participation of end-users in the animal behavior community.