At the closing scene, the garbage cruncher is chewing away, and Columbo is yelling to Clayton. Clayton reaches up to his ear and yanks down, as if ripping out his hearing aid. Moments later, he does the same thing.
When Clayton is preparing to sneak up to Dudek's room, he meets Columbo at the elevator. He is wearing his hearing aid. As he comes out of the elevator, the hearing aid is out. He hides close to Dudek's room and then walks in... wearing the hearing aid again.
When Columbo first visits Nora at her "cottage," she tells him that it had been built for her when she was a child actress. Later, when Columbo is speaking with Mr. Fallen, Fallen tells him that Al Cumberland had given the house to Nora before they were married.
During the pre-game chitchat, we hear the commentator state: "Today, all holds are barred." No idea what he means by that. The line is more usually heard as "No holds barred."