Jay Leno would like you to know that while much has changed in the world &mdash; his TV show and the landscape of network television among them &mdash; there are some constants we can count on.</p><p>&ldquo;Not only am I still married to the same woman, I&rsquo;m driving the same car,&rdquo; said Leno, glossing over that hangar full of rides he keeps in Santa Barbara, Calif. &ldquo;I&rsquo;m still living in the same house. No, I don&rsquo;t think I&rsquo;m a whole lot different.&rdquo;</p><p>And something else hasn&rsquo;t changed. Five years after Leno agreed to give up &ldquo;The Tonight Show,&rdquo; three years after he had seller&rsquo;s remorse and nine months after NBC figured out a way to keep him from jumping to another network, Jay Leno is still the most important man in television.</p><p>There will be higher-rated and higher-profile new shows this season. But none stands to have a greater impact than &ldquo;The Jay Leno Show.&rdquo; And no one better embodies the upheaval going on in this industry right now than the show&rsquo;s star.</p><p>Giving Leno the last hour of prime time every weeknight &mdash; that&rsquo;s 9 p.m. in Kansas City &mdash; to do a comedy show is a huge risk for NBC. But Leno has been proven to be as vital to the fortunes of NBC as Johnny Carson once was. Thirty years ago, when the head of the network, Fred Silverman, made noises about renegotiating Carson&rsquo;s contract, Johnny threatened to quit. End of story. </p><p>With Leno, the threat wasn&rsquo;t that he would retire but that he wouldn&rsquo;t. The idea of his jumping to ABC or Fox and undercutting the fortunes of Conan O&rsquo;Brien, his &ldquo;Tonight Show&rdquo; successor &mdash; who is already in a tight battle with David Letterman &mdash; was so frightening that NBC decided it was better to sacrifice an entire hour of prime time than to lose Jay.</p><p>Besides, have you <em>watched</em> NBC at 9 p.m. lately?</p><p>&bull;&bull;&bull; </p><p> Image control is something Leno has been practicing since he started filling in for Johnny on the Monday &ldquo;Tonight Show&rdquo; in 1986. </p><p> Viewers over 40 remember vividly what happened a few years into Leno&rsquo;s NBC tenure. He morphed from a hipster comic, working the same observational comedy as his close friend Jerry Seinfeld, into the shameless huckster who pounded the airwaves with O.J. jokes because a million more people a night preferred them to David Letterman&rsquo;s urbane monologues.</p><p>That was about the time that we started to hear a new narrative regarding Jay. Turns out he wasn&rsquo;t a happening dude at all but a hard-working lug of Irish-Italian stock, who could take apart a carburetor blindfolded and sell mirth door-to-door in much the same way that his father (that tireless father of his) sold insurance.</p><p>&ldquo;The one thing they told us loud and clear in the research that NBC did was that they don&rsquo;t want Jay to change,&rdquo; said Rick Ludwin, the longtime NBC executive overseeing late night, who appeared last month with Leno at the TV critics tour in Pasadena, Calif. &ldquo;They don&rsquo;t want us to change him.&rdquo;</p><p>But he <em>did</em> change. And America liked the new Jay. I came to appreciate his relentlessness, his pelting the audience with joke after joke after joke. For sheer entertainment tonnage, the highlights aired during the last week of &ldquo;The Tonight Show With Jay Leno&rdquo; in May simply blew away any memories I had of Carson&rsquo;s anniversary retreads. </p><p>And then for Leno to end his run on &ldquo;Tonight&rdquo; by bringing out every single child born to his staff during his 17 years as host was so sweetly amusing, it was kind of hard to imagine the guy who inflicted the Dancing Itos on the world actually thought of it.