Iiterally speaking no, because in the original sentence there is no indefinite article..
Is it supposed to mean anything? Since I think saying "It is banana" means "It is crazy" in English.
Not in Portuguese. Pointing to a fruit: "o que é isso?" "É banana!". But if you say "é um banana" you refer to a guy who is silly
My apologies, I'm having trouble following. Is it incorrect to point to the fruit and say "É uma banana"?
Is it common to ommit the subject in Portuguese like in this "É banana" sentence? Are there any rules for that?
"it is" is usually translated just as "é" or "está" (it is raining = está chovendo). The verb conjugations show us the "hidden" pronoun, so there is no need to use them, except to avoid misunderstaings, to emphasize or make distintions.
"É banana" means that you are realizing/informing someone that the previously unknown thing is a banana, or bananas, or it is banana-flavoured.
For instance, there is a piece of white ice cream whose flavour you do not know. You have a taste of it, and then, surprised, you exclaim: "É banana!".