Pretty girls and boys are the only ones allowed to sit front and center at MTV’s “Total Request Live.” Such are the words of Damien Fahey, the show’s host, while walking to lunch at John’s Pizzeria near his Times Square studio.

Just outside of MTV’s front door, he ducked past a group of young fans lined up along a half-block strip of Broadway. The crowd gathers hours before the show begins taping each weekday, and squeal in rapture once the cameras start rolling. The hour-long program tends to include Hilary Duff and Avril Lavigne videos and three-minute “chats” with ‘tween-friendly celebrities.

But when Mr. Fahey turns the corner, he’s just another 24-year-old in jeans and a Brooks Brothers shirt. Few over age 17 recognize him, at least not immediately. He aims to change that.

On Monday night, he’s guest-hosting CBS’s “Late Late Show” where he’ll introduce himself to his fans’ older siblings, if not (gasp!) their parents. Since Craig Kilborn stepped down abruptly from his hosting duties in August after five seasons, CBS has scrambled to fill his chair with a rotating series of guest hosts. So far, that list includes Tom Arnold, D.L. Hughley, and Drew Carey. But perhaps unlike some of the others, Mr. Fahey hopes the spot will lead to a more permanent gig on the network.

“I think it’d be cool to have this young, hip, late-night host that can connect with younger viewers,” Mr. Fahey said, referring to his young, hip self. “At the same time, if you get someone who’s an older guest, like a John Travolta, I’ve already interviewed John Travolta. I’ve interviewed Tom Cruise. So I think it’s a perfect match.” (Note: Mr. Travolta is 50 years old. Mr. Cruise, 42.)

Mr. Fahey has a role model, whether he will admit it or not: his “Total Request Live” predecessor, Carson Daly – one of the few MTV personalities to make the jump to the networks successfully.

As a “TRL” fan growing up in Massachusetts, “I always watched Carson and I thought, ‘What’s the big deal? Anyone can do this,'” Mr. Fahey admits. “It’s almost like he does it and it doesn’t even look like he’s working.” When Mr. Fahey took up the reins of the show, he realized the difficulty of manufacturing nonchalance while maintaining total control over the program. “The trick is to take that artificial environment and making it very natural and very organic. I think I’ve done a pretty good job at that sort of thing.”

Mr. Daly is now the star of NBC’s “Last Call with Carson Daly,” a late night show for youngish adults that features longer interviews and more live performances than “Total Request Live” (known to viewers as “TRL”). He had been the first host at “TRL,” and passed to torch to Mr. Fahey in 2002.

Mr. Fahey has been training for the “Late Late Show” job long before his MTV picked him up. He drained his savings account as a high-school student to build a radio station in his bedroom that “did everything but broadcast.” During a tour of the Springfield, Mass., FM station WMAS, he was offered an internship based on his persistent questions, and soon was hosting a call-in show.

“These 30-year-old women would call in with their problems,” he explains. “They’d be like, ‘Oh my God, I don’t think he loves me any more.’ I’m like 15, so I’m like, ‘I dunno, buy ’em a skateboard or something.'” He mentioned that he had an unusually deep voice for his age. “I soothed them with my voice and then I soothed them with the mellow sounds of adult contemporary music,” he said with a laugh.

During college in Boston, he worked as a part-time DJ at KISS 108. Once again, he rose quickly through the station’s hierarchy and soon anchored the afternoon drive. He dropped out of Northeastern University to accept an on-air job as a VJ with MTV in 2002.

He became a favorite of MTV viewers in part because of his looks, which are of the scrubbed-clean variety. “I don’t think I’m sexy,” he demurred. “The thing with television is it can convince you pretty much of anything. I bought a Swiffer off the television at 4 in the morning thinking it was going to change my life!…On television I can see where, you know, ‘He’s a good looking guy and he dresses well.’ But I have people that dress me and then I have people that put makeup on my blemishes.”

His public life is squeaky clean, too. If he is photographed out at night, he sets down his drink before saying cheese. “On MTV, your main audience is really in that stage of development where you’re learning who you are.” So Mr. Fahey tries to be “somewhat of a role model.”

That attitude toward his audience syncs with MTV’s. “It’s about kinda being part of the group,” he says of being a teenager. “You don’t want to be an outcast. Being an individual is something that [teens] really don’t want to go towards.”(He seems to never have heard that some teenagers are rebellious, angry, or in fact desperate to become individuals.)

Most of the men who have excelled as late-night hosts prided themselves on a brand of sarcasm than Mr. Fahey has yet to display on air: It’s hard to imagine Craig Kilborn gushing that “Tom Cruise is super nice.”

Then again, just as one thinks that he’s just a tad too gee-whiz for the 12:30 a.m. crowd, Mr. Fahey hints that he at least can see beyond 5 p.m. “It’s a gig, it’s a job,” he says of working at “TRL.” “You’re just trying to sell some Clearasil.”