This wasn't I Love Lucy actually, it was the Lucy Desi Comedy Hour. Anyways I forget the title, but it was the one that starred Tulula Bankhead (sorry if I spelled her name wrong). After Lucy is invited into her home later in the show, she sits in a freshly painted chair. She thinks Tulula did it and storms out. If you look closely as she leaves, there is no glass on the door to the outside. The string on the blind swings through it. Then as she's seen going past the window she brushes against the backdrop scenery and makes it flap.