The exterior shot of the asteroid which USS Voyager goes in to chase the Vidiian ship is the exact same exterior shot of the asteroid where the Enterprise-D locates the USS Pegasus in The Pegasus (1994)
This is the first of several times The Doctor uses the phrase "I'm a doctor, not a _______", a catchphrase that was made famous by Dr. McCoy in Star Trek (1966).
The subterranean Vidiian corridor was a reuse of the hidden corridor that crew members find behind a holographic barn in Caretaker (1995).
The aliens were originally known as "the Phages." Their name was later changed to "Vaphorans," which they were called even in the shooting script. The change to "Vidiians" was not made until after the episode was written.
Because the aliens of this episode were originally collectively named Vaphorans, Dereth clearly mouths the word "Vaphoran" in Voyager's transporter room; evidently, "Vidiian" was subsequently looped over it. Broadcast closed captions of this episode also use "Vaphoran". The change from that collective term to "Vidiians" was made when it was realized that no two performers could pronounce "Vaphoran" in the same exact way.