People already think I'm a cat.

With these two options paired, would that mean you think your friends are cats?

Also, based on my previous WYR, this option is happening to everyone on earth. This means that I will think that every human on earth is a cat.

I think this pairing would mean that everyone (including yourself) thinks that your twenty closest friends are cats. Interestingly, I think that would also apply to them - they'd each think the other nineteen had turned into cats. Could lead to a lot of fun confusion.

As for it happening to everyone on Earth... Yeah, I think that would mean that everyone would believe that everyone else had turned into cats. What a mess.

What friends? All I have are my cats. ._.

It actually might be more salvageable if it happens to 20 people. Because they'll all realize the other 20 are acting weird. They might figure out whats happened and be able to ascertain than the other 19 are actually people in the same predicament as them.