In making the unending publicity rounds for Girls, co-star Allison Williams has been peddling a YouTube discovery myth: Producer Judd Apatow, the tale goes, happened to come across a video of her singing a self-produced mash-up of the theme song to Mad Men in October 2010 and immediately knew that she was the actress to play Marnie, Lena Dunham's uptight girlfriend.

"He got in touch with my agents," she told the Today show last week, "and said, 'Just make sure Allison auditions because I think she has the right energy we're looking for for Marnie.' And the fact that he was able to see that in the clip was so amazing."

As the Hollywood Reporter put it, "Given the tens of thousands of videos uploaded to YouTube every day, you can imagine how few of them make their way to Judd Apatow's browser. But in late 2010, he happened to catch one mildly viral clip featuring actress Allison Williams." Williams told the Reporter, "I guess he saw something in my performance that kind of rung true with Marnie." Fate!

I'm sure the Mad Men video had something to do with Apatow's decision to seek out Williams for the role. Also having something to do with Apatow's decision to seek out Williams for the role: The fact that he knew her, and her Daddy.

The video above is of Gawker pal Brian Williams and a woman who looks precisely like his daughter hanging out with Apatow at the Nantucket Film Festival in October 2008, two years before she made the video that caught Apatow's eye. Williams senior is a longtime supporter of the festival; Apatow was receiving an honor that year for screenwriting. Williams roasted and introduced Apatow, and according to contemporaneous accounts "peppered his remarks with hilarious jabs at what Apatow's films have taught his children and how the honoree should really consider casting the newscaster's daughter in his next film."

Keep throwing up those YouTube videos, kids! It can happen to you.