If you owed your friend $20, then just pay up. Don't hate your friend for having enough self-esteem to ask for what he is owed. As for the dinners and drinks you treated him to, were you keeping score? That's fine, but let him know that you're doing that and say, "Hey, it's your turn to treat tonight. I've been keeping score resentfully throughout our friendship. You owe me 16 beers, 3 Greek dinners, a movie and 12 coffees." Do you see what he sees when you read this? yup.

See the post “There is good in the world” above.

I remember about 20 years ago when someone has owed me $20 it meant I couldn’t afford groceries.

Do you not know the difference? If one borrows money, then one is obligated to pay back the loan. A gift, on the other hand, is given freely without a sense of entitlement to have it paid back in some manner.

I think you must be a moron for failing to appreciate the difference.