Plays like "The Rise and Rise of Daniel Rocket," the fifth-season premiere of "American Playhouse" on PBS tonight, can elicit thoughts like this: "Was there ever a time in my life when I actually enjoyed this sort of thing?" Maybe when you were young and foolish, you think -- hoping that while you may indeed have at one time been that young, you never sank to being quite that foolish.

Winsome, fanciful, misty-headed and twinklingly dumb, the play, adapted for TV by its author Peter Parnell, and airing at 9 on Channel 26, presents us with yet another gooey-dewy Peter Pan figure who balks at the idea of growing up and losing his youthful innocence and sense of wonder and generally puerile outlook on life. Like Peter Pan, Donald Rocket really can fly, as he proves to his begrudgingly impressed schoolmates at the age of 12. But unlike Peter Pan, he grows up, and at the age of 32 returns to Prop Village to face the truth. Or maybe to moon the truth. It doesn't much matter.

Tom Hulce, who gave us Mozart as a giggly imbecile in "Amadeus," and who gets yet another excruciating deathbed scene here, plays the cloud-hopping hero, who declares in his childhood, "I won't ever accept less than what I want." Oh what a cruel awakening awaits this air-brained laddie in the not-so-sweet yet-to-be! And how laboriously predictable it is!

Hulce throws caution, as well as common decency, to the winds in attempting to make Donald torturously adorable. You want to leave the room. You want to leave the conscious realm. But as two of his friends, played both as children and as adults, Timothy Daly and Valerie Mahaffey make a lovely pair of lovers; Mahaffey especially finds a way to give the preciousness a little pungency. As the unflappable Mrs. Rice, Elizabeth Franz touchingly conveys the bolstering essence of Everyteacher, one of Parnell's dizzily idealized conceptions with a little credibility to it.

Flying as a metaphor for liberation of the spirit is not precisely a fresh inspiration. Bud Cort did it as "Brewster McCloud" in the Robert Altman film and, more recently, Pee-wee Herman whooshed across artificial skies at the conclusion of his stage show and subsequent, and priceless, HBO special. "Daniel Rocket" is Pee-wee Herman as Rod McKuen or Erich Segal might have written him.

One thing Donald does do enchantingly well is fly, thanks to the wizardry of flying technicians Peter Foy, David Hale and Gary Foy. Even when his hero is flying, however, Parnell won't let up on the dialogue, and director Emile Ardolino's stabs at a lyrical moment or two are hampered by the fact that those gratingly chattery characters on the ground are still letting loose with the yattata yattata yattata. Their jabbering undercuts the few sequences in the piece that have been fully videofied.

That a play ostensibly about soaring should make such an ignominious nose dive is unfortunate. There might have been a way to make it all work on TV, but not with the playwright holding on for dear life to very nearly his every word. Whatever television is all about, one realizes in the course of "Daniel Rocket," it is not all about stuff like this. 'Prince of Bel Air'

Boys, of course, would have no real desire to grow up to be men if girls did not insist on growing up to be women. The title character of the ABC film "Prince of Bel Air," at 9 tonight on Channel 7, has managed to have the best of both worlds. He is boyish and unshackled, yet the ladies love him. Frequently. Whenever, it appears, he shows up to clean their pools, which is single entendre no matter how it sounds.

His name is Robin Prince, hence the title, and as played by the young actor Mark Harmon, of "St. Elsewhere," he is both pitiable and enviable. A young woman asks him if he always lives life "like a beer commercial," and he says yes, which is something of an in-joke since Harmon is the on-air spokesman for Coors. But the kind of beer commercial being referred to is more the Lowenbrau, here's-to-acting-stupid type.

That does seem to be Robin Prince's lot in life. He plays volleyball on the beach. He picks up girls. He hangs around with a gang o' guys. Girls pick up him. But there's a telltale moment when he gazes longingly at a married friend with a child, a family man, and we know there are changes ahead.

Certainly not the kind of film that will haunt you the rest of your days, "Prince of Bel Air" still makes an affecting report on one variety of California fauna as it exists in 1986. Writers Dori Pierson and Marc Rubel have given the character a subtle poignance, and director Charles Braverman brings out every dramatic dot or compensatingly comic dash in the script. It's both funny and sad when Robin is taken to unfamiliar territory, an art gallery, and the only comment he can think of to make about the place to another patron is, "Nice track lighting."

Mainly, it is Harmon's heavy-duty charm that gives the film its oomph, and, not a moment too soon, Kirstie Alley comes along as Jamie Harris, a smart and strong-willed woman with whom Robin Prince may finally make something remotely serious of his life. In a subplot, he is also preoccupied with a likable klutz named Justin (Patrick Labyorteaux), whom one of his customers has foisted on him for the summer. It is time for Justin to lose his virginity. But not without a fight.

"Don't you ever worry that your husband's going to smell chlorine on the sheets?" Robin asks one of his clients early in the film. ABC publicity for the film tries to promise a heavy-breather, but Harmon seems an unlikely hunk (he has hair on his shoulders), and "Prince of Bel Air" is really more of a cooled-out "Alfie." Although times, to coin a phrase, change, some of the more basic moral values remain surprisingly consistent. "I'm a sensitive guy," Prince says at one point, appearing to realize he is only flashing code words, but eventually, and engrossingly, he rises to the task of proving it.