A Favor can be defined in many different ways. You can do sumone else a favor by listening when they tell you to shut the fuck up. You can also ask for a favor when you dont have any toilet paper left. The common favor asked there would be,"May i please recieve some TP?" You can also do yourself a favor by relieving yourself of bodily waste. You can say to yourself, "I Think im going to go drop the Cosby kids off at the pool." And yes that implies taking a dump. Think about that for a second...
"Hey John, i see you enjoy talking a lot during movies but can you do me a favor and shut the fuck up?"
"Hey Lou make sure you tell your wife ill return the favor for the great time last night"
"If only i did myself a favor and stopped being obese by putting the fork down"