I was going to say:
You don't know about John Holmes or Long Dong Silver do you?? Allegedly 22"
Then I read this: http://www.bizarremag.com/ask_bizarre.php?id=395
Then I thought the source was a bit iffy and found The most credible SEEMING information:
"The largest erect member in medical literature would be the 14-inch organ mentioned by Dr. David Reuben in his book Everything You Always Wanted to Know About Sex (1969). Reuben didn’t divulge any source for this figure, and there was no independent verification, so you may question his accuracy. The largest medically verified penis on record is 13.5 inches long and 6.25 inches around, documented in the early twentieth century by Dr. Robert L. Dickinson. Other sources (Alfred Kinsey, Masters and Johnson, etc.) mention specimens ranging from 9.5 to 12 inches."
And then for more information: http://en.wikipedia.org/wiki/Penis
So in all reality Mike boy is not likely 14" for 'real' but he's still size "oh my god" for most who would consider entertaining the thought of a penis in them..