Google Really Likes, Really Likes, Sesame Street: Adds Cookie Monster and Ernie & Bert

Google has seven different doodles (logos) on the day of Sesame Street's 40th anniversary. Then yesterday and today, they had two different logos, celebrating the same anniversary.

November 5th was Cookie Monster:

Today, November 6th is Ernie & Bert:

What is Google's obsession with these lovable Sesame Street characters?

Forum discussion at Google Web Search Help and Google Webmaster Help.