pull off

Hi
In the movie AI, there is a conversation that a man is talking to audience about building a robot that can dream and love and then this guy says "A robot that dreams? How exactly do we pull this off?" and the audience laugh at this...

Can you please tell me what does that mean exactly and why audience laugh at his quote?

From my understanding, it means how exactly we want to build this sort of robot... but why it's funny, I don't get it.

Thanks