How much informal writing should there be in a research article?
...funny side of my personality pops up...which I have to delete...


Good. Keep it that way. There is absolutely no place for jokes in academic writing*. This includes funny puns or things like that. The purpose of a research paper is to communicate science. Unless you are researching humour, do not do it.

What good can come out of it? Do you envision someone thinking "oh, that's a funny guy! I should hire him!"? No. This does not happen.

Jokes and what is considered good humour changes with time. Things you find funny now were not funny 10 years ago, and vice versa. Once this gets in a paper, this is forever in the scientific record. No matter how funny or witty you think you are now, you will most probably look back regretting that you did. This is also a cultural thing: things that are funny in Europe may not be funny (or even offensive) in Asia. There is also a language barrier. Some people may not even realise it's a joke and try to understand it in the context of the paper. This can only lead to unnecessary confusion.

As a reader I want to understand the science, and only the science. If you want to be funny, open a Twitter account, write a blog, post it on Facebook, put it on a poster and hang it on your office door.

*Humour is acceptable if you're a distinguished professor that made abundant contributions to science and you're writing an opinion paper. You'd have to be over 70 years old for that. And even then, use it sparingly.

Also related:


Amusing remarks in papers
Should academic papers necessarily carry a sober tone?
How much of humor in a formal academic writing is considered as disrespect?