The Owl and the Pussycat (1970)

"It's no longer a story for children."

Meek, owlish Felix and strident, catty Doris live in the same apartment building. His incessant typing bothers her; her gentlemen callers bother him. Felix informs the landlord of her activities, so Doris moves in on Felix. When they both get thrown out, they move in with Barney... until they drive him out! That's when Felix and Doris finally decide to put theory into practice. But do opposites attract?