Kermit, the Muppet frog, has gone highbrow.
There he is, his green flannel body and bulging ping-pong eyes encased in glass, near paintings by Van Gogh, Whistler, and O'Keeffe at the prestigious Detroit Institute of Arts.
Kermit even imitates, on a 13-foot silk banner outside the museum, the pensive pose of Rodin's famous bronze sculpture, ''The Thinker,'' which has long graced the institute entrance.
Kermit's purpose: to lure a Muppet-struck public inside to see the largest display ever in North America of 350 puppets of all kinds. The puppets are from two touring exhibitions that have been breaking attendance records nationwide:
* ''Puppets: Art and Entertainment'' (Puppeteers of America Inc.) traces the history of puppetry from ancient folk art to high theater, evoking modern-day nostalgia with such characters as Howdy Doody and Charlie McCarthy.
* ''The Art of the Muppets'' (Henson Associates Inc.) showcases nearly 100 characters from 25 years of TV's Muppet Show, Sesame Street, Emmet Otter's Jug-Band Christmas, and the puppet portion of Saturday Night Live.
The exhibits, augmented by films of performances and live demonstrations by the Bob Brown Puppets of Washington, D.C., occupy two floors in the museum's South Wing.
Dr. Audley M. Grossman Jr., who staged this puppet extravaganza, defends Kermit's right to go cultural. After all, he points out, puppets are an ancient art form with elements of painting, sculpture, and theater. They are popular communicators, too, so when a museum wants people to know it is displaying puppets, what better way to capture their attention than with the most popular communicator of all, Kermit the frog?
Dr. Grossman, curator of performing arts for the museum, has long been a crusader for the notion that a museum should be a ''warm, alive place'' that presents shows the general public can understand and enjoy, not a cold, intellectual environment for elitists.
He says he's happy to use Kermit's charm to draw attention to the fact that the Detroit Institute of Art has the largest collection of historic puppets in the country. It serves as the archives of the Puppeteers of America and contributed 20 percent of the puppets in the Art and Entertainment exhibit, including Remo Bufano's 100-inch puppets (from Stravinsky's Oedipus Rex); a two-headed trick harlequin (circa 1900); and three puppets from Tony Sarg (Robin Hood, 1939).
Dr. Grossman, who served as a national adviser for the exhibit, says Detroit's niche in puppetry began in 1948 when famed puppeteer-historian Paul McPharlin bequeathed his collection, papers, and books to the museum.
The current combined show, which runs through Oct. 24, spans puppet history from tiny pre-Columbian clay mannikins to a regal 14-foot-tall Queen of Spain, and from finger and hand puppets to string, body, and rod figures.