Step One: Sarcastically yell “Wow! You just pull that out of the fact hat!”
Step Two: Motion like one of your arms is wrapped bucket.
Step Three: With your other hand, pretend to pull out a little piece of paper from the imaginary bucket with thumb and forefinger.
Step Four: Now pretend to unfurl the little piece of paper with both hands as if it was rolled up and pretend to read it.
Make sure you make a retarded face while going through the steps to make the offending person feel even more stupid.