The strong resemblence of a male penis to a prawn. The size ratio is often 1:1 and sometimes can be confused with a King Prawn Willy which are extremely rare to find. The pinkish, wrinkly outer skin of a prawn displays similar characteristics of a males foreskin and the arched, horse shoe like bend of the prawn resembles the natural hanging position of a prawn willy.
"Wow, he has a small willy, looks bit like a prawn to me."
"Yea thats definitely a prawn willy!"