Dunham has been called "America's favorite comedian" by Slate. According to the concert industry publication Pollstar, he is the top-grossing standup act in North America and among the most successful acts in Europe as well.  As of November 2009, he has sold over four million DVDs, an additional $7 million in merchandise sales, and received more than 350 million hits on YouTube as of October 2009; his introduction of Achmed the Dead Terrorist in Spark of Insanity was ranked as the ninth most watched YouTube video at the time. A Very Special Christmas Special was the most-watched telecast in Comedy Central history, with the DVD selling over 400,000 copies in its first two weeks. Forbes ranked Dunham as the third highest-paid comedian in the United States behind Jerry Seinfeld and Chris Rock and reported that he was one of the highest-earning comics from June 2008 to June 2009, earning approximately $30 million during that period. Dunham also does occasional acting roles. He achieved the Guinness Book of World Records record for "Most tickets sold for a stand-up comedy tour" for his Spark of Insanity tour, performing in 386 venues worldwide.