Oh my Gosh!
Oh my god!
Oh Jeez!
Oh Man!
Oh Boy!
WHAT? You must be joking?

A: Hey I am so excited!
我好兴奋！
B: Why? aren't you always excited?
怎么啦？你总是很激动。
A: No no this time its different... I won 30,000$ in a lottery!
这次不一样！我彩票中了3万刀！
B: Seriously?! you must be kidding me.
真的吗？你在开玩笑吧！
A: Of course I am just pulling your leg you dummy.
当然咯，我开玩笑的，傻瓜。