During Mao’s Great Leap Forward (1958) and The Great Proletarian Cultural Revolution (1965-1968) the propaganda workshops worked overtime producing posters on every positive side of Communist Chinese life and Mao-worship. Smiles galore were a staple of the visual language. Let a million flowers grow and a billion smiles open wide. Smiles were even found on the Red militia, Red Guard and PLA soldiers as they were preparing to bomb their enemies. The posters here are from official how-to revolutionary manuals.
Here are more smiley posters from the International Institute of Social History.