When someone has just said something so ridiculous, so moronic, so foolish, and you can't even fathom what part of their brain spewed out that nonsensical bullshit.
*insert slow blink* "Who even are you?.. I cannot believe you just said that"
*Insert slow blink* "I'm gonna pretend you didn't just say that"
*Insert slow blink* " Are you new? Do you even go here? "