In 1975, NBC replaced its weekend reruns of "The Tonight Show Starring Johnny Carson" with a sketch comedy show starring no one of note and produced by a 30-year old Canadian whose claim to fame had been starring on a show on the CBC.

Almost 40 years later, that Canadian, Lorne Michaels, is still producing "Saturday Night Live," and now has taken over "The Tonight Show" and, with the exception of NBC's "Last Call with Carson Daly," controls the network's entire late-night slate throughout the week.

With former "SNL" star Amy Poehler's "Parks and Recreation" in its sixth season and a new series coming soon from Tina Fey, Michaels may have more influence at the network than anyone shy of NBC Entertainment Chairman Robert Greenblatt.

"He is the guiding vision of late night television," said Ron Simon, a curator at the Paley Center for Media. "He was the young lion who came in to overturn the comedy establishment and now he's become the comedy establishment."

The move gives Michaels control over two franchises that have long determined what is considered the mainstream of comedy.

A tight five-minute set on "The Tonight Show" has traditionally been a rite-of-passage for a stand-up comedian, while "SNL" has launched the careers of many of comedy's biggest movie stars.

With "The Tonight Show," "Late Night" and "SNL," one man now has a great deal of sway over what one network believes to be funny. Based on Michaels' track record, that can be a blessing, but as the recent uproar over the show's diversity (or lack thereof) has shown, it could also be a curse.

"If there is any 'danger,' it's that the comedy profile for the network is defined by one man's instincts," said Gerard Bocaccio, a longtime TV executive, producer and associate arts professor at NYU.

Giving Michaels the keys to the late night kingdom, though, makes sense for NBC, considering the disaster that took place the last time NBC tried to transition "The Tonight Show."

Over the past decade, NBC has looked repeatedly to Michaels to help transition Saturday night talent into time slots during the week, whether it's an "SNL" writer like Emily Spivey, who created "Up All Night," or starring vehicles for Tracy Morgan ("The Tracy Morgan Show") and Fey ("30 Rock").

"Some of this has to do with a comfort zone, and dealing with someone that you know has your back," Bocaccio said. "He's worked there for a tremendous amount of time, and they went to him and said, 'We're giving you the crown jewel. Please take care of it.'"

That "jewel" can seem like a heavy burden from the outside. But, as Simon pointed out, it may be no more onerous than that of the show that put Michaels on the map back in 1975.

"Everyone's been talking about the 50 or 60 years of 'The Tonight Show,'" Simon said, "but it's been pretty close to 40 years of 'Saturday Night Live.' It's got its own tradition now, too."