A title only the mosy highly honored dishwashers ever claim. Its got a connotation relevant to those of Napoleon Bonaparte and Alexander the Great. Seldomly will you ever meet one.
Despite claims this phrase originated on "The Simpsons", it actually existed long before it was used in the show. The phrase is intended to portray the distortion of facts when passed from person to person.
Its use in "The Simpsons" was accurate; Bart starts a rumour by whispering to one person who whispers it to another, etc. By the time the rumour reaches the front of the crowd, the phrase "Purple monkey dishwasher" has been added to the end due to people mishearing the original rumour as it passed from person to person.
Due to the popularity of "The Simpsons", the phrase has since become a commonly used response to opinions stated based on hearsay and unconfirmed rumours.
Person A - "I heard from a friend of a friend that John cheated on Linda with Karen!"
A person who collects used condoms and cleans them out by effectively sucking the semen from the insides.
Mikey: Don't talk to Tommy, that guy's a Boston Dishwasher.
Franky: What's that?
Mikey: He sucks cum out of condoms like cocaine residue from a Ziploc bag