Usually using the guise that they didn't hear or understand you, this is becoming extremely common.
Hard to defend against, but sometimes just waiting a minute or calling their bluff may win the day.
you: "hey dude what happened to that cute girl you were gonna ask out"
you: "i said where's that cute girl that you were.."
staller: "o that GIRL, she died"
you: "fuck off you heard me the first time"
you: "hey would it be okay if I went and finished that job?"
staller: "what did you say?"
you: "you heard me"
staller: "yeah, no that would be a good idea"