For balance, let me first share a few that newly arrived foreigners say:
"I'm going to revolutionise the way the Chinese think/do business/learn/speak/view themselves..."

Earth to stupid: you're not going to change anything. In fact, China's going to change
you.
"Chinese is going to become the world's language." (It's a valid and interesting argument, but most new arrivals have no idea how to support this statement after they drop it. For a laugh, try asking them why they think this.)
"I'm going to open a language training center." (Said in a pretentious and knowing tone two days after arriving.)
"I've got guanxi with
(insert a government body here)." No, dipshit. You don't.
I also can't stand the way new foreigners often up their act in public because they think they have an admiring audience. It's just grating to watch.
I guess the top of my wtf China conversational moments include anything said with regards to Yue Zi (that month after a woman gives birth when she's expected to refrain from showering, brushing her teeth, eating spicy food, getting out of bed, ...).
And these tidbits:
"I don't drink coffee because I don't want my skin to darken."

"My stomach isn't comfortable." (Your coworker says this to you when they need to take a dump.)

"How much money do you make?" (Said twenty seconds after meeting this person for the first time.)
"Do you like Chinese girls?" (Said by a coworker you've just met. Or by a coworker you've known for years. Either way, it's unprofessional and just out of place in the office.)
"Foreigners don't love their children." (Said upon viewing a foreigner that won't allow their screaming two year old to have a candy bar at grocery checkout."
"Wow, you've lived in China X years. You must like China better than your own country."