You can always pick the comedian out of a crowd in a restaurant; he's the one with the funny hat.

"I don't know about you," says Michael Keaton, "but I'm certainly wearing my napkin." And with that he places his folded white linen square directly atop his brown, dry-look hair, assumes the posture of a nurse and has the waiter laughing hysterically.

"Very easy to work a room like this," Keaton says, his green eyes beaming. The timing is perfect. The room happens to be almost empty, as does the catsup bottle, which he turns upside down and pounds upon. Again, the waiter laughs. And he doesn't even know this guy gets paid to be funny.

Nor for that matter do a whole lot of people -- even some of the ones who saw him act in a short-lived TV series called "Report to Murphy" or the mini-series "Studs Lonigan." As Keaton himself says, "How funny can three weeks of drunken Irish guys feeling sorry for themselves be?"

But things have been picking up for the man who stole the show from Henry Winkler in the movie "Night Shift," wherein he makes an entrance sure to be remembered as a cimema classic: Beneath the headphones of his Walkman, Keaton saunters into the New York City morgue screaming in harmony with the guitar riff of the Rolling Stones' "Jumpin' Jack Flash." It is while working on the night shift at this same morgue that Keaton stumbles upon a unique financial opportunity.

Winkler: Do you realize that we are running a prostitution ring out of the New York City morgue?

Keaton (slamming his fist down on the desk): Is this a great country or what?!

There's an even daffier side to Keaton. It was his idea to improvise a scene in the film in which a blind man approaches Winkler and Keaton for spare change, and Keaton writes the guy a check. "There are certain ironies in life I like to think about," he says. "I've always wanted to be in an airport and hear a page: 'Will Joey Heatherton please call Connie Stevens.' They're interchangeable."

A few days ago, Keaton took several hours off from a schedule that included appearing on the David Letterman television show, getting ready to host tonight's edition of "Saturday Night Live" and preparing for his second film, "Mr. Mom," to talk about his career. "I want to make some money -- do it for another 10 or 15 years and then retire to Montana and trout-fish," he says.

"I grew up outside Pittsburgh in a town called Forest Grove. My father was a civil engineer. He died a few years ago. My mother had six other children. I'm 31. I'm the youngest. I have an older sister close to 50, and 20 nieces and nephews. I'm the only kid who doesn't have any children, and I can feel the pressure all the time.

"When I was a kid, I was very funny and kind of nuts. I knew I could never keep a job like other people have regular jobs. And look how I wound up making a living! Everybody in my family was pretty funny -- funnier than me. My mother is in her early seventies, and you ought to see her do pratfalls. But even in grammar school I was too scared to get on stage. Still, I used to act all the time for myself. I used to read fiction -- famous escape stories, guys in prison in World War I -- in my bed and I wanted to talk the dialogue. I didn't want it to sound like television. That was another whole world to me that had nothing to do with reality. I had these fantasies about being Jimmy Cagney coming home from World War I to a ticker-tape parade or getting up to bat in the bottom of the ninth and hitting a home run. It sort of came true a couple of weeks ago. I had lunch at the Palm in Los Angeles. I'm on my way to the table and a bunch of waiters start clapping for me and are quoting lines from 'Night Shift.' It felt great.

"When I got out of school I drove a cab in Pittsburgh for a while, and I worked as a Good Humor man. Then I got a job on the production crew at the PBS station. They were doing this show on mental illness and I volunteered to play the crazy person.

"God, I was so good at it. I realized I'd better try to be a comedian. So I started to hit the improv clubs. I did some very strange things. I used to have this rubber chicken on a gum band and make him dance. And I'd play a guitar case. I decided I ought to get serious about this and I moved to L.A.

"When I got out there I'd sit in my room for days and write. Then I'd go off to places like the Comedy Store. You have to earn your spot. You think you have 10 minutes of great material, and then you get on stage and 30 seconds of it works. So I'd go back and write more. I also tended bar at the Figaro Restaurant on Melrose and I parked cars in the Valley.

"I worked in Tahoe once and Vegas once. The first night in Vegas was the lowest point in my career. You reach a point where you think you're bombproof and then, kaboom. I experienced that total panic, a sickening feeling. Words are coming out of your mouth and they're not your own. There was absolute silence and then this one drunk guy in the back of the room was clapping once every three seconds. I walked off and I was blind.

"At once point I decided to stop everything I was doing -- which was nothing -- and put about $1,500 into a little film I wanted to make. It was 3 1/2 or 4 minutes, about a kid sitting in school. The teacher is giving the class a problem, a time-distance problem. If a man leaves Cleveland and a man leaves Los Angeles and they're both heading for Duluth, where do they cross paths and how much time will it take them? The kid starts to work the problem, and one guy's car comes to a stop and you see him go into a phone booth. Then the teacher comes up to the kid and tells him he's got a phone call. It's the guy in the car, and he tells the kid that his car has broken down and he'd better adjust his computations.

"I guess at some point I decided I wanted to be in films. I was in 'Report to Murphy,' playing a parole officer in Cleveland. It was brilliant. This girl who was the prom queen comes back to town as a hooker and I had to be this passionate guy. I did 13 episodes of 'Working Stiffs' with Jim Belushi. I had a running role on 'Mary Tyler Moore,' a running role on 'All's Fair,' two shots on 'Tony Randall.'

"Now I'm about to do this film 'Mr. Mom.' It was written by John Hughes from the National Lampoon, and Stan Dragoti, who did 'Love at First Bite,' is going to direct. I play Mr. Mom, a guy who loses his job in Detroit and is forced to become a housewife in a middle-class family. The craziest part about all this is that my wife, Caroline McWilliams, is a much better actor than I am, and she's at home and I'm out working.

Keaton is scribbling notes to himself as he talks, trying to get some gags ready for his Letterman appearance. "I get to a point before I work," he says, "when I just have to be alone. Sometimes it's hard to be funny." And with that he wanders off and disappears into the lobby of his hotel.