When Brazilians want to say that something unexpected came up, they do it like this:
"Aconteceu um imprevisto!"
Which just seems strange for two reasons: 1) The verb is at the very start of the phrase; and 2) where is the 'came up' part?
(from Semantica Series 2: advanced dialogs)
A beginner would try and say this more literally and likely end up with: 'Alguma coisa imprevista aconteceu'. And this wouldn't be wrong, but it wouldn't be the way it's actually said here in Brazil.
Let's break it down:
1) Brazilians often place the action verb at the beginning of a sentence:
> Acabou que ele não foi à festa porque estava chovendo.
> Fez muito sol ontem.
> Conseguiram vender o apartamento.
2) PREVER is the verb 'to predict'. PREVISTO/A is of course, unpredictable.
A few variations on this sentence are:
> O imprevsito aconteceu. (the unexpected happened)
> Acontece o imprevisto. (the unexpected happens >> 'shit happens' 😉