Why do pets fake limp when they see their owner injured? I have seen many videos where cats and dogs will limp when their owner has a hurt or broken leg. Why is this?
If it’s a dog, it’s in sympathy. If it’s a cat, they are mocking you. Just kidding.
Lots of animals copy behaviors they see, even if they aren’t particularly social. It’s normal behavior that helps adapt to complex situations because they can learn from each other.
It’s empathy. Mirroring behavior is a way of signaling membership in a group and saying they want to be like you.
I had a dog who would fake limp when she had done something wrong. 
After we were in a really bad accident, our dog would limp. She was sweet and would avoid where we were injured.
When I broke my foot and had to use crutches, my Shih-Tzu would limp with me. It was touching.
Videos on social media are often staged or trained for effect.
It’s a trained behavior. Not a hard trick to teach if you have training skills.
Many videos contain manipulated content. We need to critically evaluate what we see.
It’s funny to copy the human. My dog will fake a limp if he’s done walking, but that limp disappears once we get to the car.