Nearly a hundred works on paper, almost all from the sixties, might seem a timely amuse-bouche for the huge retrospective of the German artist, who died in 2010, that opens at MOMA this month. But they’re a banquet in themselves. What a mind was Polke’s! Every picture, be it a ballpoint scrawl or a densely worked gouache, uncorks some singular idea about art, popular culture, or uncharted philosophy. Serious joking alternates with throwaway profundity. (Sample titles: “Beer Coaster Fountain,” “Why Can’t I Stop Smoking?,” “Everybody Is His Own Car,” “Painted at the Command of Higher Powers.”) Assessing Polke’s greatness is a priority today, but no cinch. How do you honor someone who, when not dancing away from your comprehension, laughs in your face? Through June 7.