In the juvenile novelty act ''Puppetry of the Penis,'' the two naked performers Simon Morley and David Friend spend about an hour onstage manipulating their genitals (not each other's, happily) into shapes more often associated with balloon animals. Then they give their constructs (''installations'' is their word) names -- the Eiffel Tower, the hot dog, etc. -- and the combination of can-you-believe-this audacity and fifth-grade wit sends enough audience members into groans and hysterics to encourage the boys to continue.