Appearing in "Proteus - Part I"
- Professor X (Charles Xavier) (Main story and flashback)
- Wolverine (Logan)
- Beast (Dr. Hank McCoy) (Main story and flashback)
- Cyclops (Scott Summers) (Only in flashback) (Cameo)
- Iceman (Bobby Drake (Only in flashback) (Cameo)
- Angel (Warren Worthington III) (Only in flashback) (Cameo)
- Marvel Girl (Jean Grey) (Only in flashback) (Cameo)
- Proteus (Kevin MacTaggert) (Main story and flashback) (First appearance)
- Joe MacTaggert (Main story and flashback) (First appearance)
- Morph (Cameo)
- Amelia Voght (Only in flashback) (First appearance)
- Technet (Cameo)
- Ian (Only appearance)
Synopsis for "Proteus - Part I"
The long hidden secret patient of Muir Island, a reality-warping mutant teen known as Proteus, escapes from his 15-year long captivity, and wreaks havoc across Scotland searching out his father.
- Technet, the interdimensional mercenary group from the comic "Excalibur", makes a cameo in the Muir Island pub (apparently the same mutant-filled one as in "The Cure"). Their roster here: Ringtoss (the yellow round-headed guy), Gatecrasher (the big blue woman), Yap (her shoulder-pal), Waxworks (the red squid-thing), Ferro (the furry-headed one), Scatterbrain (the green girl), China Doll (the light-blue lady), Joyboy (the small floating blob), Thug (the red & black shouldered creature), and Bodybag (the green snake-like guy).
- The original five X-Men are shown in flashback, marking the first time Angel is officially revealed to have once been a member of the team. Iceman, a pre-furred Beast, and Cyclops are wearing their yellow & blue school-uniform spandex, while Angel and Jean Grey are wearing their second, more-individualized costumes.