LOS ANGELES (AP) _ In a town where St. Elsewhere is far better known than St. Vibiana, the patron of the cathedral, actor-playwright Pope John Paul II found himself on the Universal lot only a couple of hours after his limousine rolled past huge letters on the hillside emended to read ''Holywood.''

On a floodlit sound stage seemingly borrowed from a TV game show, and with wild applause to match at the mention of various home towns, the pontiff ''dialogued via teleconference,'' as TV anchors called the new liturgical rite, with young people popping up before him on a huge screen from Portland, Ore., Denver and St. Louis.

Tony Melendez, a young folk singer who was born without arms, stole the show and the pontiff's heart by accompanying himself barefoot on the guitar.

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''The pope is to the left, the studio tour is to the right,'' usher Cedric Dillard bawled through his bullhorn at the crowds coming into Universal City.

The pontiff passed within a grenade throw of the ''Miami Vice'' thrill show, but passed up the flaming speedboat chase and stuntmen's derring-do in favor of delivering a moral message to media moguls at a nearby hotel.

What became the hottest ticket in tinsel town, because of the limited seating in the hotel ballroom, brought out Bob Hope, Charlton Heston, Phil Donahue, Dom DeLuise, Dino De Laurentiis. Lew Wasserman, head of Music Corp. of America, emceed the meeting.

The ever-prying TV cameras caught a few of the glitter gulch's more glittering residents either deeply moved or zonked out while the former star of Krakow's Studio 39 players held the stage.

The pope called on the communications industry to promote human dignity instead of appealing ''to what is debased in people'' with violence and pornography, and to be a force for moral uplift.

''In a nutshell,'' commented Loretta Young, ''he asked us to please, please, clean up our act. And it's time we did it. I was impressed.''

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If John Paul II had consulted the latest Variety, the show biz bible, instead of L'Osservatore Romano over his morning croissants as Shepherd One flew into Los Angeles, he would have known that he wasn't the only pope making news in Hollywood.

Right in the middle of the papal visit, Charles Durning was making his debut tonight as Pope John XXIII in ''I Would Be Called John,'' a 90-minute docudrama on public television. And Albert Finney, looking remarkably like the visitor from Rome, could be seen giving a blessing from the windows of several downtown video shops offering his semi-documentary biography of John Paul II.

The pope, who visited England at the same time his play ''The Jeweler's Shop'' was closing in the West End, had better luck in movietown. The film version, starring Burt Lancaster, was scheduled for release at the end of the year.

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The sacrifice of the Mass is perhaps the world's longest running and most widely attended religious drama, but in Hollywood, you have to have a warm-up act.

The church called on Ann Jillian, Ricardo Montalban and gospel singer Sandi Patti set the stage for the pope's outdoor celebrations at the Los Angeles Coliseum and Dodger stadium.

Hollywood glitz even intruded on the pope's morning prayer agenda at nearby San Fernando Mission, which the TV faithful were sure to recognize as setting for many movie and TV productions like ''The Love Boat,'' ''Falcon Crest'' and ''Pee Wee's Great Adventure.''

Also ahead on the papal run up the California coast was a meeting with the mayor of Carmel, Clint Eastwood, who got his start in Rome in ''spaghetti Westerns'' about the time a young Polish bishop so impressed Curia cardinals that he was asked to perform as retreat master for Pope Paul VI.

Back then, neither could have imagined they would star together on ''Dirty Harry'' T-shirts bearing the inscription, ''Thou Hast Made My Day.''