The Pennsylvania Academy of the Fine Arts has been invaded by a street artist named KAWS.

The classical paintings in the historic Frank Furness Building on Broad Street now are interspersed with day-glow abstractions and 6-foot-tall fiberglass cartoon characters.

One of the hard-won treasures in the PAFA's collection is Benjamin West's "Death on the Pale Horse." The 25-foot-long painting depicts the Four Horseman ravaging the earth with war, famine, pestilence, and death.

PAFA acquired it in 1817 by mortgaging its own building. Then the building caught fire. Firemen rescued the enormous canvas by cutting it from its burning frame.

Now, it's partly obscured by three cartoon sculptures -- all variations of KAWS' iconic "Fake Companion" -- placed in front of the painting. The violence of "Fake Companion," as a cartoon figure with half its skin flayed to expose its bones, muscle, and viscera, draws attention to the surprisingly violent Four Horseman of Benjamin West.

"Someone who is well-versed in art can walk in here and see Eakins and tell his background, and you have these young kids who know every sneaker of the last decade and what came first and what styles were influenced by what," said KAWS, who came into this world as Brian Donnelly. "Everyone thinks their own pocket is most important."

Philadelphia's first installation by KAWS, last spring, was a temporary sculpture in the 30th Street train station of a mouselike cartoon figure sitting with his hands over his eyes. Now, PAFA has scattered KAWS'  pop-art pieces throughout the permanent collection.

The connections between the old and new are accidental. Nevertheless, they're hard to miss. A fluorescent day-glow painting mimics the nearby illuminated stained glass windows by the early 20th-century artist Violet Oakley. In another gallery, KAWS hung dozens of cartoon paintings in a dense salon style that exactly echo the 19th-century paintings on the opposite wall. It forces the viewer to closely scrutinize everything -- the "SpongeBob SquarePants" abstractions and the collection of classic portraiture.

KAWS did not intend any of these effects; they just happened upon installation. The cartoon imagery he draws from, such as "SpongeBob SquarePants" and "The Simpsons," have a universal impact, he said.

"You can be anywhere in the world and somebody would know Homer's 'Doh!' " said KAWS. "You can not even speak the same language, but grow up with these cartoons like background."