I'm nobody.
我是無名小卒。
I'm somebody.
我是大人物。

chatty = someone who talks a lot
愛說話的人
Jack is a chatty person.
Jack是一個話很多的人。

messy = someone who is very untidy
I'm not a very messy person.
我不是一個不愛干凈的人。
You are a compulsive cleaner.
你是一個清潔狂。
You are such a screen junkie.
你是一個玩手機上癮者。

A couch potato is a lazy person who spends a lot of time sitting down or lying down, watching TV, playing video games, or doing some other activity that doesn't involve physical activity.
Couch potato指的就是很懶的人，成天躺著或者坐著，看電視，玩游戲，從不鍛煉。
Jack is a laid-back person.
Jack是一個悠閑的人。
Mumu is an affectionate person.
木木是一個多愁善感的人。