The X-Men were voiced by the same actors from the X-Men: The Animated Series (1992) animated series. However, since this show records the voices with all of the actors present, it had been expensive to get the "X-Men" voice actors to fly via airplane from Canada to Los Angeles to record their dialog for "Spider-Man".
Although she is listed in the voice actors cast list, Catherine Disher does not provide the voice of Jean Grey in this episode as Jean doesn't speak at all. In fact, Jean is only seen once in the entire episode when Beast explains to the other X-Men who just arrived about what happened to Herbert Landon.
Beast admits his early work was about trying to eliminate his mutantcy and a brief flashback shows a human looking Dr. Hank McCoy. This would make sense with his flashback appearances on X-Men as Hank McCoy started to become blue and furry as a teen but tried to look a bit more human as he did in flashbacks with the original 5 X-Men. Beast wanting to look more human was one of the themes in the "Spider-Man: Mutant Agenda" comic mini-series.
This episode is based on "Spider-Man: The Mutant Agenda" #2 - #3.
With the introduction of the X-Men, every time the team comes together for a battle, you can hear in the background the opening credit music from the TV series "X-Men: The Animated Series" (1992-1997)