Thanks to Paul for the picture
The X-Men team appeared in their civilian outfits in the season 2 episode "Nightmare in Green." They showed up when Johnny Storm and Rick Jones were going around the city in the Pogo Plane. The Juggernaut appeared briefly a second afterword, so they were probably looking for him.
Spider-Man
All of the X-Men appeared in the season
2 episodes "Mutant Agenda" and "Mutant's Revenge." Storm also guest-starred
during season 5 of Spider-Man, during the Secret Wars 3 parter. She was not
voiced by Alison-Sealy Smith, but instead, by Iona Morris, the original voice
of Storm.
Silver Surfer
This doesn't really count, but many of the
X-Men voice actors supplied voices to the Silver Surfer cartoon. Some of
them are: Norm Spencer (Cyclops) did Drax, Cedric Smith (Xavier) did Mentor,
Alyson Smith (Jubilee) voiced Amber, James Blendik (Apocalypse) voiced Galactus,
Don Francks (Sabretooth) voiced a Kree soldier, David Hemblin (Magneto) voiced
a Skrull soldier, Mark Strange (Forge) voiced Lord Glenn, Alison Sealy-Smith
(Storm II) voiced Gamora, and that's just the tip of the iceberg.
This page is a part of DRG4's Marvel Cartoon Pages:
Featuring Spider-Man, X-Men, Fantastic Four, Iron Man, Incredible Hulk, and the Silver Surfer.