In ANH I always thought that the line was "Negative, Negative. It didn't go in. It just pecked in on the surface."
Adam corrected me and it is "impacted on the surface." Huh. I did not know that.
Another common one for me grown up was "Gentlemen wastes time to be traveling lightly." When it really was "The Juttland wastes are not the be traveled lightly."
And I recently found out what the hell Han Solo said in ROTJ when he goes "Mumble mumble" and Luke says, "Yeah, she coming up." He actually says "Got her warmed?" refering to the emperial ship.
What other lines have you confused as something else?