I Love You, Alice B. Toklas! (1968)

Peter Sellers stars as Harold Fine, a self-described square--a 35-year-old Los Angeles lawyer who is not looking forward to middle age and his upcoming wedding. His life changes, however, when he falls in love with Nancy, a free-spirited, innocent, and beautiful young hippie. After Harold and his family enjoy some of her "groovy" brownies, he decides to "drop out" with her and become a hippie too. But can he return to his old life when he discovers that the hippie lifestyle is just a little too independent and irresponsible for his tastes?