When Trip and Lorian are working in engineering (14:30), one of the tools that Trip takes from the toolbox and puts back is actually a Radio Shack decibel (or sound level) meter. It has a short cylindrical protrusion and upper curved edges. This carries on a tradition of using Radio Shack gadgets for Star Trek props. In the original series one of the props was a Radio Shack tape head demagnetizer - having a long, thin light-up wand of clear plastic so you could see into a dark area around recessed tape heads.
The squared representation in the episode's name (²) can be visually considered as half a character, making "E²" visually shorter than Star Trek: Voyager: Q2 (2001) by only half a character and the shortest episode title in the "Star Trek" franchise.
T'Pol and Tucker, who were married, albeit in an alternate timeline, have the first Human-Vulcan hybrid, Lorian. His ultimate fate remains unknown, be it dead, alive or erased from history. His conception was made possible after Doctor Phlox found a way of combining the Vulcan and Human genomes. This foreshadows the events in Star Trek: Enterprise: Terra Prime (2005), where the DNA from T'Pol and Tucker is used to create the "first" Human-Vulcan hybrid, Elizabeth.