As a smile stole across his face, Dr. Billington, 74, added, "Belushi going down that food line sort of spoofed a whole way of life."
This praise wasn't meant to impress his grandchildren. Instead, in a recent interview, Dr. Billington brought up "Animal House" to try to explain why he had accorded it a singular honor, one he has also given to other American movies as varied as "Casablanca," "Abbott and Costello Meet Frankenstein," "Citizen Kane," "Lassie Come Home," "Gone With the Wind," "This Is Spinal Tap" and "On the Waterfront."
At first glance they are films you might never expect to see mentioned on the same list, maybe even in the same breath. But over the years all have been named to the National Film Registry of the Library of Congress, in essence landmarking them much in the way that the government has landmarked the Hoover Dam or the Brooklyn Bridge, the primary aim being to help to ensure they are preserved.
The library recently added another 25 movies to the registry — an eclectic list that includes "Young Frankenstein," "Patton," "Tarzan and His Mate" and "Tin Toy," an early Pixar short — bringing the total number to 3 75. It is also in the final stages of a multimillion-dollar plan to consolidate, by next year, all of its film preservation efforts and film and television holdings — the world's largest, with more than a million items — in a huge underground bunker near Washington originally built to shelter federal bureaucrats during a nuclear attack.
As it enters its 16th year of giving a stamp of government approval to pieces of cinematic history, the library is also seeking greater public understanding of how it decides to declare a movie a "national treasure." So a day was spent recently with Dr. Billington and his staff, watching them watch movies, talk about movies, obsess over movies and try to demystify the yearly process, often painful, of winnowing the names of hundreds of movies down t o just 25.
It is a job in which they are helped by a board of professional movie lovers from around the country, including academics, critics, cinematographers, producers and archivists who sort through the possibilities, many submitted in letters and e-mail messages from ordinary taxpaying movie buffs.
Ultimately the decisions come down to Dr. Billington and his staff, who must face the inevitable Monday-morning-quarterback questions, sometimes in the halls of Congress: O.K., so "High Noon" and "The Godfather," sure. But "Night of the Living Dead"?
And if "Night of the Living Dead," why not "The Texas Chainsaw Massacre"? If "Dog Star Man" by the avant-garde filmmaker Stan Brakhage, why nothing yet by Andy Warhol? And if "Animal House," why nothing yet by John Waters or Harold Ramis?
As the list grows larger and more inclusive every year, so do those kinds of questions, and the library's film staff and advisers try to consider them all, adhering to Congress's 1988 mandate that the library choose films not only for their aesthetic value but also for historical and cultural reasons. (A film cannot be considered until at least 10 years after its release.)
"It's not the Academy Awards," Dr. Billington likes to say.
John Ptak, a member of the National Film Preservation Board, which helps the library select the films, says the job is difficult because the goal is nothing less than choosing the movies that best express American culture, and that of course is a slippery concept.
"Culture is not just an uptown concept," he said. "We address the popular as well as the classics and the avant-garde in very lively conversation. There are definitely a number of strong opinions around a rather intimidating table."
He added that as far as he was concerned, " `Animal House' is just as representative as Welles, Brakhage or Flaherty." (Robert Flaherty directed the classic documentary "Nanook of the North.")
Both the board and the library, as an organizing principle, are very conscious of categories, Mr. Ptak said. Are there enough science-fiction movies? Are there enough movies from the teens? Enough cartoons? Enough documentaries? Are there more home movies that deserve inclusion? (In 1992 Congress broadened the Film Preservation Act by dropping the requirement that only feature-length films with theatrical releases could be included. The Zapruder film of the John F. Kennedy assassination is one of several homemade movies now on the list.National Film Registry lists are online at www.loc.gov/film/.)
In some cases the cultural value of a movie is determined the old-fashioned way: simply by listening to the public. For example, in December, after years of impassioned pleas from fans of Nelson Eddy and Jeanette MacDonald, the library added "Naughty Marietta" from 1935, the first pairing of these two stars, whose movie operettas have not had quite the staying power of other musicals from their era.
"We've made a lot of Eddy-MacDonald fan clubs very happy," said Steve Leggett, the library's staff coordinator for the preservation board, as the lights went down and MacDonald's birdlike soprano filled a screening room deep inside the library. (He added that "Hoosiers," the 1986 high-school basketball feel-good movie, was also added in 2001 because of the overwhelming number of requests for it in letters and e- mail messages from the public.)
Besides "Naughty Marietta" the films put on the projector that day for a visitor were a kind of representative sampling of what the library tries to do every year.
There were firsts like "Tin Toy," the first time a character with lifelike features was successfully animated digitally, and "Princess Nicotine, or the Smoke Fairy," a five-minute silent short from 1909 that was the special-effects pioneer of its day. Using double exposure, stop-motion animation and mirrors, the film makes it appear as if fairies are hiding inside a man's pipe and dancing near his Sweet Caporal cigar box. ("A 1909 film with dazzling special effects and product placement," Mr. Leggett pronounced. "How modern can you get?")
There was also "One Froggy Evening," one of the most revered Warner Brothers cartoons ever made, which joins two others — "Duck Amuck" and "What's Opera, Doc?" — to complete a kind of shrine to the animator Chuck Jones. And there was raw film from Fox Movietone News in 1928 of the Jenkins Orphanage Band in Charleston, S.C., a brass band that produced several notable jazz musicians, among them the trumpet players Jabbo Smith and Cat Anderson, both of whom played with Duke Ellington.
"When people talk about the archaeological value of film preservation, it's this kind of footage they're talking about," said Gregory A. Lukow, the chief of the library's Motion Picture, Broadcasting and Recorded Sound Division, whose eyes were fixed on the screen. "The historical importance of films like this is tremendous." (In some cases the library restores and preserves registry films itself or makes money available; in other cases the attention given to a film on the list attracts private funds for preservation.)
It quickly becomes clear in watching movies with the library's film staff that they are as much buffs as academics. During a snippet of "Gold Diggers of 1933," a musical choreographed by Busby Berkeley, Patrick Loughney, another of the library's movie experts, pointed out that a bellhop who made a brief appearance had a familiar voice for a good reason: he was Sterling Holloway, who later went on to provide the reedy voice for Winnie- the-Pooh in animated films.
The staff also noticed, for the first time, that one of the signature songs sung from "Naughty Marietta," "Ah! Sweet Mystery of Life," is briefly sung by Madeline Kahn in "Young Frankenstein," which was also named to the registry in December.
"We love those kinds of coincidences," Mr. Leggett said, smiling contentedly.
If they have any regrets about a job in which they are paid to watch movies, the film experts said, it is that they rarely have time to watch any as amateurs anymore.
"And the other problem in this job is that you never get to watch anything to the end," Mr. Lukow added sadly, as a Busby Berkeley musical suddenly went dark before the big dance number. "It's always Reel 6 or 7 or 8, but not the whole thing."