In 1990, Lucasfilm Games released a classic adventure game called "The Secret of Monkey Island." It was an excellent game, and it introduced the world to the continuing exploits of the most hilarious pirate who ever lived. But one of the more hilarious parts of the game was a scene involving the main character buying a ship from an energetic salesperson named Stan, who became a recurring character in the series, famous for his flapping arms and his oddly patterned jacket.

In 2006, a YTMND user by the name of "Torico" Created the site "Stan Sells EVERYTHING to Guybrush," which shows a looping Animation of the Salesman accompanied by the Weird Al Yankovic song "Hardware Store." Seen below is a video of the song (not official)

The site became popular on YTMND, gaining over 443,000 views as of June 2010, and spawning several parodies, usually with either different animations, different audio loops, or with an interruption.
A list of some follows:

Stan Bores Picard

Stan Stalks Guybrush

Drug Store Sells EVERYTHING to Ness

Stan Sells EVERYTHING to Guybrush -The Game!

Stan Sells Religion and Politics

Stan Sells an Incredibly Long Sentence to Guybrush

Guybrush shuts Stan Up

A Capella Stan

Stan Sells EVERYTHING to EVERYONE

And Here's a list: YTMND search: Stan

There are also a few Team Fortress 2 YouTube examples:

Sniper Sells Everything to Scout:

Engineer Sells Everything to DemoMan:

Believe it or not, this meme is one of the most famous YTMND fads ever, but on the rest of the internet, it could use some attention.