Henry's Night In (1969)

Nerd who can't satisty his wife creates formula to turn invisible so he can spy on his sexy neighbors in their beds. His shrink advises him to have sex with a lot of different women to regain his ardour. His wife invites all of the neighborhood hot wives to a party which Henry ruins be releasing a pack of invisible guinea pigs! This causes the women to strip off their clothes and run into the street where they are arrested. The wife goes to the same shrink who hypnotises her into stripping and having sex with him. She discovers his secret but forgives him now that he can get it up again. Ironically, she spends a lot of time at home walking around naked, which should have cured him of his hang-ups. All of the girls are volupuous and full frontal nude babes. A voyeur's delight