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.
Alan Young (David Filby/James Filby) is the only actor to appear in both this film and the remake, The Time Machine (2002).
Rod Taylor's first leading role in a major film.
The shape of the time machine itself was inspired by one of George Pal's favorite types of childhood vehicles - a sled. This is the reason for the sled-like design of the machine, so that it could "slide" into time.
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.