I just learned about the Avis rental car cleaning fee, that they can arbitrarily charge your credit card, and you can do nothing about it after they hit you with it

 so be sure to get someone at your rental can company to look over your car before you officially turn it back in, and get them to write a note declaring how it's not going to be hit with a cleaning fee. 

the guy who told me about this did not have a cat in the car, but he did stay with his daughter, who has cats, and he suspects that the hair transferred off of clothes to the seats. 

And just like that, poof, 80 dollars out of his paycheck