Interesting Customs Differences

Two different things happened to me today that would unlikely happen in the U.S.
THING NUMBER ONE: Business Being Conducted at a Metro Stop
So there is this insane festival in Valencia on Friday called Las Fallas. People from Valencia spend the entire year building fallas or giant paper mache sculptures/floats/models. This year the theme is "el crisis" and there supposedly will even be fallas of the first family. Anyways at midnight on Friday all of the fallas will be set on fire and burned as fireworks go off all over the city.
This is an internationally known festival and therefore it is extremely popular to go to. Thus waiting until two days before to find tickets leads to an interesting story. I used the everhandy services of google and found a trip with Madrid Erasmus that still had spots left. Only my instructions for paying were to go to a metro stop and pay in cash! This is something that would be considered extremely shady and I would never do at home...but I'm not at home right. I have a receipt and the people seemed legit so hopefully it all works out but I was very nervous to do this initially.

THING NUMBER TWO:The Grocery Store
So I went to the atm to get cash today because I needed to and walked away with a fifty euro bill. Walking around with a fifty bill isn't the most practical thing though so I wanted to break it. I also needed some snacks from the grocery store. My total came to 1.35 and I paid 50.35. The cashier seemed annoyed when I paid with a fifty then confused when I gave her change. In the U.S. it's fairly common to give change when you overpay to make the amount you receive back nicer. I don't think that's all to common here because this isn't the first time I've been given a very confused look when paying for something.

That's all for now. On to la crema de las fallas! (That's what it's called when the burn everything :D)