Stan and Kyle express their dislike for the ending of Contact (1997), just like Mr Garrison did in Tom's Rhinoplasty (1998). This actually reflects Trey Parker and Matt Stone's well-known negative opinion of the movie.
This was originally intended to be the 100th episode of the series, but it wound up airing as the 97th instead. However, if one includes "Jesus vs. Frosty", "Jesus vs. Santa" and South Park, le film : Plus long, plus grand et pas coupé (1999), then this is indeed the 100th story in the South Park universe, making all of the references to that landmark, in a way, still legitimate.
As the first episode following Kenny's return in "Red Sleigh Down", this episode establishes the new convention that Kenny no longer dies in every episode.
When the aliens/visitors are present, there is a recurring three-note musical cue borrowed from the alien-themed video game Super Metroid (1994).