JERRY MATHERS will be 10 years old forever. As Theodore "Beaver" Cleaver on "Leave It to Beaver," Mathers was an icon of freckle-faced all-American boyhood, always in trouble, always able to get out of it with a high-pitched, stuttered "Gee, Wally . . . "

"I've been an actor since I was 2 years old," says the 34-year-old Mathers, who still resembles his youthful alter ego. Mathers began his career as a "Calendar Baby" for a department store, then worked with Ed Wynn and Spike Jones in television shows like "Lux Video Theater." He was spotted there by director Alfred Hitchcock, who cast him as Shirley MacLaine's son in "The Trouble With Harry" at age 4 1/2. Several Bob Hope movies followed, including "The Seven Little Foys," and it was on to immortality as "The Beaver."

"I was with the show for seven years, and we did 39 shows a year. That makes 200 or something," Mathers says about the longevity of the gentle family situation comedy.

"I think the reason it lasted so long is that it was wholesome, and about real life at the same time," Mathers says, attributing that quality to writers Joe Connelly and Bob Mosher who created the series. And every episode had its moral, of course. "Ward always comes on at the end and explains it all to Beaver and Wally," Mathers says. "For our time, we were very, very provocative. We had a show about divorce and one about alcoholism."

The show has been the subject of wicked parodies on programs such as "SCTV," "Saturday Night Live" and WWDC radio's Howard Stern show, whose "Beaver Breaks," featuring the Cleavage family and a Beaver for the '80s, is syndicated to several cities.

There is still "a tremendous amount of interest in 'Beaver' out there," Mathers says. "I probably do about four telephone interviews a day, and lots of personal appearances, at shopping malls and stuff. Someone called me the other day and wanted to talk to me about a new cult on campus called 'Beaver for God.' You have to drink root beer once a day, ridiculous things like that . . . "

Life after "Beaver" was pretty average. Mathers became a "normal high school kid" again. "I had a rock band, too, called Beaver and the Trappers.Our record was a number one hit in Alaska and Hawaii," Mathers says.

Mathers went to Berkeley for a degree in philosophy after stints in the Air Force and National Guard. While there, a rumor started circulating that nags him to this day. "The rumor that I died started with the wire services," Mathers says. "They used to scan the casualty lists, and some editor saw the name and printed it without checking. It was very strange. People sent flowers to my parents' house. It's hard to combat something like that."

After graduating, he worked as a commercial loan officer for a bank, then as a real estate agent in Los Angeles' then-booming market. "I planned to go back into acting," says Mathers.

And so he did, going on the road with Tony Dow, who played big brother Wally, playing dinner theaters in a comedy written especially for them called "So Long Stanley."

Mathers says he does a lot of television work now, mostly made-for-TV movies and commercials. "I did the 'Lily Tomlin for President' special for CBS. I was the the expectant father you kept seeing on the moviola." He also has a radio show Sunday evenings on KEZY, Los Angeles, called "Jerry Mathers Gathers, With Rock and Roll for Mind, Body and Soul." Mathers and his second wife, Rhonda, and children Tori, 10, Noah, 4, and 5-week-old Mercedes, live in a Los Angeles suburb.

Mathers still keeps in touch with the rest of the Cleaver clan. Barbara Billingsley (June Cleaver) is working as an actress. "She did that funny bit in 'Airplane!' and played an ax murderess on 'Mork and Mindy.' And she's on the Richard Simmons show a lot." Hugh Beaumont (Ward) died recently after a long illness.

As for the neighborhood kids, Ken Osmond, who played obnoxious Eddie Haskell, is now a motorcycle cop in Los Angeles. "There was a rumor going around that Ken was John Holmes, the porno star," Mathers says. "Ken has been suing the distributors of the movies. There was a blitz of posters saying 'With the star of 'Leave It to Beaver.' "

Stanley Fafara, who played Whitey, Beaver's best pal, is now "a real-far-out artist person in Philadelphia, with that white hair down to the middle of his back.

"Things are looking real, real good for a sequel to 'Beaver,' " Mathers says, with a touch of the old eager Beaver enthusiasm. "All the same characters will be back. A network has accepted a script for a two-hour pilot, and they told me we could be in production by fall. I think people are ready for us again."