I'm a Brasilian developer and I'm currently looking for reallocation to another country. For that, I need a cover letter for my resume, but Brasilians tend to be playful and not that formal even on cover letters - don't get me wrong, we can treat serious situations seriously when needed -.
My question is: when presenting myself to an European (for example) employer through my cover letter, is it better for me to be all serious or to make some respectful jokes and talk about stuff that doesn't really matter for the job (Example, talking about how I am deeply inserted to the culture on England because my 3 favourite pop culture things are from there - Doctor Who, Harry Potter & Sherlock Holmes-)