Strong Guy (Guido Carosella) Created by Chris Claremont and Bill Sienkiewicz, Strong Guy first appeared in New Mutants volume 1 #29 (July 1985).
Multiple Man (James Arthur "Jamie" Madrox) Created by writer Len Wein with script from Chris Claremont and art by John Buscema, Multiple Man first appeared in Giant-Size Fantastic Four #4 (February 1975).
Polaris (Lorna Dane) Created by writer Arnold Drake and artist Jim Steranko, Polaris first appeared in X-Men #49 (October 1968).
Quicksilver (Pietro Django Maximoff) Created by by writer Stan Lee and artist/co-writer Jack Kirby, Quicksilver first appeared in Uncanny X-Men #4 (March 1964).
Havok (Alexander "Alex" Summers) Created by writer Arnold Drake, Don Heck, and Neal Adams, Havok first appeared in Uncanny X-Men #54 (March, 1969).