Lichtenstein painted a Mickey Mouse for his children and one of them said 'I bet you can't paint as good as that.' He took the challenge literally. By 1961 he was making paintings that looked like enlarged comic book panels: thick black outlines, flat primary colours, Ben-Day dots visible as if through a printer's magnifying glass. The art world had no idea what to make of them.

He was not young when this happened. He was thirty-eight, teaching art at Rutgers University, and had spent the previous decade painting Abstract Expressionist canvases that looked like everyone else's. The comic paintings were a deliberate rejection of the idea that art had to show the artist's inner emotional state. They showed Donald Duck instead.

Leo Castelli gave him his first show in 1962. Every painting sold before the exhibition opened. The speed was unusual. Warhol was doing similar things with soup cans and Coca-Cola bottles, but Lichtenstein's method was different: he hand-painted everything to look mechanically reproduced. The Ben-Day dots were applied through a stencil. The lines were drawn with a projector and then painted by hand. The process was laborious and precise, which was the joke: meticulous craftsmanship in the service of something that was supposed to look cheap.

He moved beyond comics into landscapes, brushstrokes (paintings of brushstrokes), Chinese landscapes, interiors, and nudes, all in the same flat, graphic style. The Brushstroke series, where he painted enormous images of painterly brushstrokes in the same deadpan comic-book technique, annoyed Abstract Expressionists specifically and delighted everyone else.