Roy Lichtenstein was one of the first American Pop artists to achieve widespread renown, and he became a lightning rod for criticism of the movement. His early work ranged widely in style and subject matter, and displayed considerable understanding of modernist painting: Lichtenstein would often maintain that he was as interested in the abstract qualities of his images as he was in their subject matter. However, the mature Pop style he arrived at in 1961, which was inspired by comic strips, was greeted by accusations of banality, lack of originality, and, later, even copying. His high-impact, iconic images have since become synonymous with Pop art, and his method of creating images, which blended aspects of mechanical reproduction and drawing by hand, has become central to critics' understanding of the significance of the movement.
Art had carried references to popular culture throughout the 20th century, but in Lichtenstein's works the styles, subject matter, and techniques of reproduction common in popular culture appeared to dominate the art entirely. This marked a major shift away from Abstract Expressionism whose often tragic themes were thought to well up from the souls of the artists; Lichtenstein's inspirations came from the culture at large and suggested little of the artist's individual feelings.
Although, in the early 1960s, Lichtenstein was often casually accused of merely copying his pictures from cartoons, his method involved some considerable alteration of the source images. The extent of those changes, and the artist's rationale for introducing them, has long been central to discussions of his work, as it would seem to indicate whether he was interested above all in producing pleasing, artistic compositions, or in shocking his viewers with the garish impact of popular culture.
Lichtenstein's emphasis on methods of mechanical reproduction - particularly through his signature use of Ben-Day dots - highlighted one of the central lessons of Pop art, that all forms of communication, all messages, are filtered through codes or languages. Arguably, he learned his appreciation of the value of codes from his early work, which drew on an eclectic range of modern painting. This appreciation may also have later encouraged him to make work inspired by masterpieces of modern art; in these works he argued that high art and popular art were no different: both rely on code.