It vs This, that etc
I don`t understand when I can use 'it' and when I can use 'this'.
I watched Madagascar and King Julien tell lemurs: 'keep Mort out. It`s so annoying'.
What did Julien mean 'Mort is so annoying (He is annoying)' or 'This is so annoying'?
I just don`t know how say better. 'This will be cool' or 'It will be cool' when I mean a event will be cool.

Question

It vs This, that etc
I don`t understand when I can use 'it' and when I can use 'this'. 
I watched Madagascar and King Julien tell lemurs: 'keep Mort out. It`s so annoying'.
What did Julien mean 'Mort is so annoying (He is annoying)' or 'This is so annoying'?
I just don`t know how say better. 'This will be cool' or 'It will be cool' when I mean a event will be cool.

Answer

Both are correct.
This will be cool (the experience will be cool).
It will be cool (the event will be cool).
More info needed to understand conversation from movie  but it seems he is saying this is so annoying.

Answer

Oh.. tough question to explain !!!