The shape of the silicon-based ship-eating parasite is that of Lambda phage, a virus which infects E. coli bacteria.
When Ensign Kim and Derran Tal hook up in the shuttle, Derran says there is a nebula about 300,000 km away. That's about the same distance from Earth to the moon.
First appearance of Seven of Nine's all-blue bodysuit.
Charles Rocket (who plays Jippeq) played a character named Commander Riker in A Leap for Lisa - June 25, 1957 (1992). Quantum Leap (1989) starred Scott Bakula, who would go on to star as Capt. Jonathan Archer in Star Trek: Enterprise (2001), originally titled "Enterprise."
This takes place in 2375.