It's an oldie, but 1 of my favs :

QA expert decides to go out and have some fun. He walk for a whle spots a random bar and gets inside. After a solid 10+ minutes just looking critically arrond he dicides to stay. Goes to the barplot and orders :
- One beer por favor!
- Here you go - says the barman and continues his job. The man drinks it up quickly and orders again :
- 3 more beers ahora mismo!
- Enjoy - says the barman while serving them.

a few moments later...

- Hey barman, last order and we can round the night up, what ya say?
- ok - simply replies the barman.

- -5 beers!