I thought I was just being funny or just kind of being a smartass.

我以为我只是在搞笑或者只是在耍小聪明。

Okay, smartass, which one am I?

好吧 小机灵鬼 我惯用哪只手？

If you say: " He is being a smartass." it means maybe just this one time.

如果你说：“他是个聪明人。”这意味着也许只有这一次。

So if you say: " He is a smartass." it just means that's his character.

所以如果你说：“他是个聪明人。”这只是意味着那是他的性格。

A smartass is a person who tries to be funny, but they do it in kind of a not nice way.

聪明人是一个试图搞笑的人， 但他们这样做的方式不太好。