This guy is (a?) pretty chill person.

[sitifan]

This guy is pretty chill person. (at 1:57 of the video below)

Is the quoted sentence grammatically correct?

 

[probus]

It needs "a" before "chill" and the indefinite article is clearly there. It is perfectly grammatical slang.

 

[jutfrank]

This is a transcript of what he says:

Or this guy? Looks like a pretty chill person, eh?

The subject of the second sentence is missing but that's fine in such an informal register.

As probus says, the subtitle, which is not what's said, is ungrammatical without 'a' before chill person.

 

[Skrej]

You could omit the article if you also dropped 'person'.