If you're bored and looking to entertain yourself for a few minutes (LOL OK, hours), face swapping is a wonderful way to do it.
Using Snapchat's face swap filter, you can trade mugs with anything that has a face. Bestie swap? Sweet. Couple face swapping? Cute. Swapping faces with the Starbucks logo? Hilarious. But when you bring your pet into it, shit gets weird, and I'm pretty sure you aren't going to sleep for days after seeing this.
You were adequately warned. Proceed with caution.