 Complete the following phrase:  Many Super Bowl advertisements have become iconic and well known because of their quality, unpredictability, humor, and use of special effects. In recent years, advertisers have also attempted to stand out from others by producing ads with cinematographic qualities, and ads that channel emotions and real-world issues. The use of celebrity cameos has also been common in Super Bowl ads, ranging from then-unknown personalities to unexpected combinations of celebrities, such as a 2007 CBS network promo for Late Show that featured David Letterman and Oprah Winfreywhom Letterman had conflicts with following a joke directed at her during the 67th Academy Awards, and a 2010 sequel that also included Jay Leno who was slated to return to its competitor, The Tonight Show, following a 