This poster combines several Glaser hallmarks: groups, large planes of color, iteration and gestural line. In many ways it recalls the poster for The Shadowlight Theater, with varied coloration in place of the monotone suggestion of flickering light. But probably its closest neighbor stylistically is 100 Ways To Have Fun With An Alligator (also around the same time, 1970) which also exhibits a thin contour line and shifting gradient fill that draws the eye down the length of the poster. (In Milton Glaser Graphic Design, he describes using the Split Fount technique for the gradient effects of this period — applying multiple inks on each roller of the press.)
You can study the various poses more easily in the larger version here.
Only a few of the figures appear in prior sketches, but they end up being used almost verbatim (look closely!).