Alan Young (David Filby/James Filby) is the only actor to appear in both this film and the remake, The Time Machine (2002).
Yvette Mimieux was actually underage when shooting began (she turned 18 during the shoot) and was not legally supposed to work a full shooting schedule, but did. She was inexperienced, but as she worked on this film she kept getting better and better, so that by the end of the shoot the producers went back and re-shot some of her earliest scenes.
According to supplemental information on the DVD George Pal wanted the disk on the machine to spin clockwise for travel into the future and counter-clockwise for travel into the past. Due to the way the mechanism was built it was deemed too expensive and time-consuming to add the reversing feature.
The globe in the background when George is listening to the information rings was used in Forbidden Planet (1956) as the navigation sphere.
There is also a large circular screen in a square panel on the wall which was in the cruiser Control Deck beyond the sphere.
In the DVD special feature entitled "Time Machine: The Journey Continues" FX designers Wah Chang, Tim Baar, and Gene Warren state that the scene of the tree limb with several apples and leaves growing on it at an accelerated rate while George moves forward in time was actually a painting done by artist Bill Brace. The canvas was photographed with a locked-off camera, one frame at a time, as Brace rendered the progressive growth of the leaves and apples in great detail.