I'm a bit new to this, so please bear with me...

I simply just took the sprites of the dog and replaced them with Arcanine. The sprites themselves originated from the GBA game, Pokemon Mystery Dungeon which was created by Nintendo. I simply modified them to be more Stardew Valley friendly, which by that I mean I just altered them slightly to "fit" the box in which the dog animations take place. Was more of a pain than anticipated, but I got it to work! I also modified them to make the Arcanine's sit animation more smooth and "natural" looking.

I actually originally did this to use the Arcanine as a "base" for another project, but since I went through all the hassle, I figured others would like to use these and have their own Arcanines within Stardew Valley. Making them shiny was a simple color swap. 

I did, however, not include a scratching animation... Looking at the dog sprite sheet, I didn't notice there was really one at the time of making these and, since I never had a dog on my farm before, didn't realize there was an animation. So there will be a thumping noise, but Arcanine will just be sitting there. If anyone wants me to "fix" this issue, then I'll be happy to do so! I personally didn't care, so I didn't bother.

Feel free to ask me for other sprite swaps! It might take me awhile to get to them, thanks to my "busy" schedule, but I enjoy creating sprites and it helps me practice for possible larger projects in the future.

Since this is a simple sprite swap, all you need to do it unzip the file, copy the file and replace it with "dog.xnb" under "Animals" within the "Content" folder of your Stardew Valley game. REMEMBER TO SAVE YOUR ORIGINAL "dog.xnb" FILE SO IT DOESN'T BECOME LOST! Jut in case you ever want to go back to vanilla.