Origin

Ellen Feiss is the 15 year old girl appearing in this Mac Switch ad from 2002:

Internet Phenomena

Her half-drugged looking gestures and funny expressions made her instantly an internet celebrity.

In parallel with the main Apple Switch parodies phenomenon, Ellen Feiss got her own set of parodies taking place in altered pictures but, mainly, in Youtube videos:

You can find more here

A peculiar theme discussed among fan was to know if Ellen really was or wasn't "stoned" during the shooting.
In an interview from november 2002, Ellen Feiss commented on her fame and explained the circumstances behind the ad and her funny stoned looking behavior:

It doesn’t really bother me. I do admit to
looking pretty out of it in that commercial -- I
think I look horrible. It was after school, but I
was the last person to make the commercial, so
by the time I made it it was like 10, so I was
really tired. The funny thing was, I was on
drugs! I was on Benedryl, my allergy
medication, so I was really out of it anyway.
That’s why my eyes were all red, because I
have seasonal allergies. But no one believes
me.

Furthemore, she was the subject of a documentary episode from Culture Chain:

You can even find here soundbytes from the original Ellen Feiss lines.

Elsewhere

She got so popular on the web that Fan club websites entirely dedicated to her tribute have been created:

• http://www.ellenfeiss.net/
• http://ellenfeiss.gloriousnoise.com/

Finally, there are 3 YTMND instances of her:

• http://ellenfeiss.ytmnd.com/
• http://ellenfeisspooter.ytmnd.com/
• http://nothingthatwittytoday.ytmnd.com/

Maintream career

In 2006, Ellen starred in a French movie called Bed & Breakfast :

That news got many articles from fans and The Digital Lifestyle, an online 24 hour video channel dedicated to Apple, aired that film in 2008.