"Conan" is ready to go (Updated)

Now that the Jay Leno era has come to a close, it's time for Conan O'Brien to step in.

Beginning tonight, Conan O'Brien becomes the fifth host to front The Tonight Show in the program's 55-year history, following Steve Allen (and Ernie Kovacs, who hosted the Monday and Tuesday episodes of "Tonight" during the Allen era), Johnny Carson, and Jay Leno.

Tonight also has a new executive producer (Jeff Ross), a new band (Max Weinberg from O'Brien's Late Night show), and a new set at Universal Studios' backlot in Universal City, Calif., where NBC Universal is basing its West Coast operations.

O'Brien's task now is to fill big shoes again - like he did in 1993 when he replaced David Letterman as host of Late Night. His tenure wasn't always successful: Critics gave the series poor reviews, and ratings were subpar. His show was dumped by NBC affiliates in Houston, Detroit, and Buffalo in the mid-1990's before they returned him to the air, albeit in the wee hours of the morning. However, the show finally hit its stride by the end of the decade with ratings growth in key young-adult demos.

Now with O' Brien taking over as host of Tonight, his competitor in fact, is Letterman - he has hosted CBS' Late Show for sixteen years, the same duration O'Brien spent on Late Night.

One thing going for the former Simpsons writer is the fact Tonight has been the No. 1 late-night franchise since its inception, with the exception between 1993 and 1995 when Letterman was on top.

But O'Brien faces a much different late-night landscape than Leno did when he first took over Tonight in 1992 - he has not only Letterman to contend with, but other options such as The Daily Show With Jon Stewart, The Colbert Report, Jimmy Kimmel, and Adult Swim.

In addition, TBS is throwing its late-night hat in the ring by hiring George Lopez to do a 10 p.m. (CT) talk show beginning in November.

When O'Brien started with Late Night in 1993, his contract was only renewed thirteen weeks at a time. Now that he is hosting The Tonight Show, he doesn't have that worry anymore.

Or does he?

Updated at 10:09 p.m.