Answer by Mimiwhatsup: Well is actually depends there is the Laughing Dog File where there is a bunch of pictures of laughing dogs and then there is the extension. The extension is actually for a game that people played back in the day called 'Cat's and Dogs'. File extension DOG is mainly used to organize and store digital images. The .dog file is a Graphic Images/Arts which is a Laughing Dog Screen Maker screen saver file.