The vent that Rob hears the voice only appears in this episode.
In the toy shop, near the end of the episode, an exposed-brick wall can be seen upstage left. Although redressed, it's clearly the same wall from the Petrie's dining room, suggesting that the set was constructed in front of the Petrie living/dining room set. In fact, the door to the kitchen can be seen just left of the wall.
The property master, Glenn Ross, included his name on the directory board outside of the writer's office. He used room 163 as his office number.
The fiberglass UFO prop was repainted and used on the Jack Webb series Project U.F.O. (1978-1979). In 2021 the prop was sold at auction. As of 2023 It has been sitting in the Vintage Coin Op Restoration warehouse waiting to be fully restored to the original Dick Van Dyke Show condition and painting and will be displayed in the Bilotta Museum in Ponte Verde Beach Florida when completed.
Around the two-minute mark when the camera moves from Rob with his feet up in the air to Buddy, the camera shakes.