Tonight, a jittery Conan O'Brien will replace Jay Leno to become the fifth host of The Tonight Show, while Leno's new gig, The Jay Leno Show at 10 pm, will revolutionize primetime. O'Brien's spacious new set hearkens back to the Johnny Carson era, and according to The New York Times, the first show will have Pearl Jam and Will Ferrell as guests. For his part, Jay Leno's new 10 pm talk show may be "among the most pivotal changes since the network evening newscasts were expanded to 30 minutes, from 15, in1963." Leno's new primetime show will save NBC millions of dollars, as it costs a fifth as much as its scripted drama competition. Depending on how Leno does in this time slot, other networks may follow suit.