Earl A. Powell III, director of the National Gallery of Art, toured the latest show in his museum 10 days before its opening.

Workers were still adding the final touches as he made his way through the exhibition. In the last room, as he took in the paintings, he noticed, out of the corner of his eye, a young woman with long blond hair, jeans and running shoes admiring a work by Belgian surrealist Rene Magritte.

“Have you met the courier from Cincinnati?” called out Mark Leithauser, the gallery’s director of design. Powell, an outgoing man known to his staff and friends as Rusty, turned to greet the young woman. As he did so, Leithauser burst into laughter. Powell had been hoodwinked. The young woman was “Portrait of Kim,” an incredibly lifelike sculpture created by American artist Duane Hanson in 1996.

Hoodwinking the customer -- even the museum director -- is the main point of the exhibition, “Deceptions and Illusions: Five Centuries of Trompe l’Oeil Painting,” which is on view at its sole venue, the National Gallery, until March 2. Trompe l’oeil is a French expression that means “deceive the eye,” and it is used to describe a genre of painting in which the artist tries to fool the spectator into thinking that the depicted object not only looks real but is real. For this show, the National Gallery has added several sculptures like those of Hanson that try to do the same thing.

The exhibition mixes art history with a little bit of P.T. Barnum and Harry Houdini. Even when you know what you’re seeing is meant to deceive, you still get fooled.

Organized by guest curator Sybille Ebert-Schifferer, the exhibition makes clear that the sharpest practitioners of such deception were a group of 19th century American painters led by William M. Harnett. Ebert-Schifferer, who is director of the Bibliotheca Hertziana at the Max Planck Institute for Art History in Rome, had been astounded by these artists when she attended an exhibition of American art 20 years ago. That eventually led to her scholarly interest in trompe l’oeil and the invitation by the National Gallery to mount this show in Washington.

Although trompe l’oeil didn’t get its French name until 1800, illusion and deception have long been a tradition in painting. Roman historian Pliny the Elder wrote that classical Greek artist Zeuxis painted a bunch of grapes so well in the 5th century BC that birds swooped down on the canvas and tried to eat the fruit. Another painter, Parrhasios, then showed Zeuxis his own canvas, seemingly covered by a lace curtain. When Zeuxis tried to pull off the curtain to see the painting, he discovered to his embarrassment that the curtain itself was the painting.

These paintings have long been lost in antiquity, but Pliny’s story has inspired artists since the Italian Renaissance to try their hand at deceptive grapes and curtains. “Ghost Clock,” a contemporary sculpture by American Wendell Castle, fooled most people at the show. It looks like a 7-foot-high grandfather clock partially wrapped in a white sheet, but, in fact, the entire sculpture, including the sheet, is carved mahogany.

Another kind of crowd deceiver is Louis-Leopold Boilly’s painting “A Collection of Drawings.” He coined the term trompe l’oeil, and his contribution here looks like a pile of prints and drawings packed beneath broken glass. On opening day, gallery goers continually pointed out the damage to each other and some even argued that it was real.

In the 13th century, according to legend, Italian artist Giotto enjoyed painting little flies on his canvas and then watching his master, Cimabue, try to shoo them off. This story inspired later Italian artists to do likewise. In the exhibition’s 16th century portrait of “Cardinal Bandinello Sauli and Three Companions,” Sebastiano del Piombo tries his hand at the same deception. Over the years, even National Geographic and several scholarly journals have tried to improve their reproductions of the painting by air-brushing out what they assumed was an interloping insect.

There are many good “fooled you” stories here. Harnett’s work was so realistic that U.S. Treasury agents once seized his painting of a $5 note because they thought he had counterfeited the bill and then glued it onto the canvas. His “After the Hunt,” painted in 1884, hung in a saloon on Broadway in New York for many years while drunkards and out-of-towners wagered whether the hat, horn, rifle, rabbit and birds were real or paint.

In my own favorite in the show, Harnett’s contemporary, Jefferson David Chalfant, painted a 4-cent stamp alongside a real 4-cent stamp in the early 1890s and then added what looks like a real newspaper clipping that reads, “Mr. Chalfant pasted a real stamp beside his painting and asks, ‘Which is which?’ ” I couldn’t tell.

Trompe l’oeil has long been derided by the art establishment. “If the excellency of a painter consisted only in this kind of imitation,” 18th century British portrait painter Joshua Reynolds said, “painting must lose its rank.” John Ruskin, a 19th century British critic, deplored its limitations: “We can paint a cat or a fiddle, so that they look as if we could take them up but we cannot imitate the ocean, or the Alps.”

Still, there are enough works by painters such as 17th century Spaniard Bartolome Esteban Murillo and the 20th century Magritte to make it clear that even the finest artists have employed trompe l’oeil. Pablo Picasso, whose work is included in the exhibition, turned the genre on its head by creating collages in which papers were pasted on canvas to make them look as if they were painted.

But Ebert-Schifferer believes that the quality of trompe l’oeil has been underestimated. She maintains that the genre’s power comes from a tension between reality and illusion that is “a visual reflection of scientific and philosophical uncertainties.”

Standing in front of the artworks, amid the smiles, guffaws and oh-my-goshes, the critical debate hardly matters. Whether or not they’re great works of art, the paintings and sculptures in the show are all great fun.