Gates McFadden did all her stunts for the vortex effects sequences. Shortly after performing the stunt where she is thrown from Data's ops console chair, McFadden learned she was pregnant.
This story originated as a subplot for Family (1990), in which crew members were to have disappeared due to a wormhole. However, it was felt that there was not enough room for both plots, so the premise was developed as a separate story.
The Traveler's make-up was modified slightly for his second appearance. Here, and in Journey's End (1994) his make-up appears much paler than in his first appearance in Where No One Has Gone Before (1987).
Eric Menyuk (the Traveler) originally auditioned for the role of Data, only to be beaten out by Brent Spiner.