If the world does end on Wednesday, as some have said it might, or even if it ends at 11 p.m. today, at least television will have gone out with a bang: "Night of 100 Stars," an absolutely unmissable three-hour ABC special at 8 tonight on Channel 7.

Actually, 202 stars show up one way or another on the program, a benefit for the Actors' Fund taped Feb. 14 at Radio City Music Hall. For the TV version, a running tally has been helpfully superimposed throughout the show so viewers can keep count. Orson Welles, for instance, is No. 3; Howard Cosell is 31; Lillian Gish is 58; Lola Falana is 101; Mary Tyler Moore 165; Lynn Swan 169; Al Pacino 183; and Sandy, the dog from "Annie," is 202.

Some stars only stroll across the stage, but this doesn't seem a cheat, because just to see some of them again amounts to either inspiration or edification or both. Gregory Peck looks great; Bette Davis looks great; Van Johnson and June Allyson look great; Robert Sterling and Anne Jeffreys look great; Alexis Smith looks great; Mary Martin looks great; and Ethel Merman, er, sounds terrific.

The stupendousness comes from having all this luminescence in the same place at once; having Helen Hayes and Gene Kelly and Paul Newman and Lauren Bacall and Ben Vereen and Brooke Shields and James Stewart all in such close proximity. A sequence on fun couples reunites the likes of Alice Faye and Don Ameche, Howard Keel and Jane Powell, Anthony Perkins and Janet Leigh (from "Psycho"), Ruth Gordon and Bud Cort ("Harold and Maude") and, as a fittingly lustrous modern-day capper, Warren Beatty and Diane Keaton.

New York Mayor Edward Koch, in tails, playfully leads off a spectacularly overpopulated medley of Broadway reprises by the original stars--Robert Preston singing a snippet of "76 Trombones" again, Diahann Carroll cooing "The Sweetest Sounds," and Mickey Rooney and Ann Miller doing an irresistible turn from "Sugar Babies" that radiates professionalism and pizazz and will probably sell hundreds more tickets all by itself. Even a medley paying tribute to current stars of television comes off classily. And any show that includes a duet by Placido Domingo and Miss Piggy commands a certain respect. Placido: "Miss Piggy, do you miss your frog?" Miss Piggy: "What frog?"

The single most moving moment by far occurs when, as the finale to a sequence featuring movie stars of then and now, James Cagney rises up out of the stage seated in a chair and the audience, 5,000 strong, simultaneously rises in tumultuous ovation. Cagney is so struck by this display that he chokes up, even begins to weep--an incredibly emotional, spontaneous high point that the director, Clark Jones, cuts away from with flabbergasting stupidity.

Also, near the show's conclusion, a final parade of celebrities includes Lee Strasberg, who taped the segment before his death.

The production was undertaken by Alexander H. Cohen to raise money for the Actors' Fund centennial celebration. A running history of the past 100 years, intelligently written by Hildy Parks, is elegantly spoken throughout the program by Princess Grace, Elizabeth Taylor, Jane Fonda, Jason Robards, James Earl Jones and others.

In reassembling the show on tape for televsion, the producers were able to eliminate or disguise clinkers and boondoggles that beset the stage production. All flows smoothly here, though certain baffling choices were made. After a high-kicking opener by the Rockettes, and some dumb continuity for the TV audience, the first act is a wan ditty by the Doobie Brothers, who are dour just when the show needs zip.

Film clips used to introduce the movie stars include, back to back, Gregory Peck talking about "a quiet humble Negro" in "To Kill A Mockingbird" and Ginger Rogers declaring, "I'm free, white and 21" as "Kitty Foyle." Didn't anyone have the sense to see how offensive such lines are when taken out of context?

Almost everything else is either splendid or forgivable. Doug Henning saws two women in half and puts them back together in a very novel way; Robin Williams is hilarious describing the Music Hall as "the Sistine Chapel as designed by Francis Ford Coppola"; porky Christopher Cross whines out "Arthur's Theme" with Dudley Moore at the piano; and Liza Minnelli leads the New York Yankees through an electrifying chorus of--what else?--"New York, New York."

"Night of 100 Stars" is a magnificent conception that proves even on television a fabulous pip.