Mercury (Cessily Kincaid) is a fictional character from Marvel Comic's X-Men series.
 She is a teenage member of the student body at the Xavier Institute and a recurring member of the X-Men.
Wither (Kevin Ford) is a fictional character, a mutant appearing in comic books published by Marvel Comics.
 He has been a member of the student body at the Xavier Institute, a member of the Hellions training squad, and a supervillain as a part of Selene's Coven.
Gentle (Nezhno Abidemi) is a fictional character, a mutant appearing in American comic books published by Marvel Comics.
 The character has been depicted as a member of the student body of the Xavier Institute.
Tag (Brian Cruz) is a fictional character appearing in comic books published by Marvel Comics.
 He first appeared in New Mutants, vol.
 2 #7 and was a member of the student body of the Xavier Institute and the Hellions squad therein.
The Stepford Cuckoos are a set of fictional mutant psychically linked quintuplets (Celeste Cuckoo, Esme Cuckoo, Irma "Mindee" Cuckoo, Phoebe Cuckoo, and Sophie Cuckoo).
 The alphabetical order of the Cuckoos' first names corresponds with their ages, with Celeste being the firstborn and Sophie being the youngest.
 Originally calling themselves the Five-in-One, with the deaths of Esme and Sophie the remaining sisters are now known as the Three-in-One.
Hellion (Julian Keller) is a fictional character, a mutant appearing in American comic books published by Marvel Comics.
 He was a member of the student body of the Xavier Institute before its closing and is a member of the X-Men's training squad.
Surge (Noriko "Nori" Ashida) is a fictional character, a mutant in the Marvel Universe, one of the student body in the Xavier Institute, and a member of the former New Mutants squad therein.
 She maintained her powers post M-Day and was the leader of the New X-Men.
"Imperial" was the second story arc from Grant Morrison's run on the Marvel Comics title New X-Men, running from issues #118-126.
 It further explored the origin behind the character Cassandra Nova as well as giving more depth to the student body at the Xavier Institute, specifically the Stepford Cuckoos, Beak, and Angel Salvadore.
Icarus (Joshua "Jay" Guthrie) is a mutant superhero.
 He was a member of the student body at the Xavier Institute and a member of the New Mutants training squad.
 Jay was the son of Thomas and Lucinda Guthrie.
 Thomas dies early in Jay's life due to black lung, developed from working in local Kentucky coal mines.
 Jay's older siblings Sam (Cannonball) and Paige (Husk) are mutants as well, and both have been members of the X-Men.
 When he himself developed mutant powers, he hid them from his family.
 However, when performing in his band, playing guitar, he exposed his wings to the crowd as a 'stage gimmick'.
 Believed to be descended from the ancient race of Cheyarafim mutants.
 Icarus possesses red-colored, feathered angel-like wings which allow flight and produce extensive regenerative enzymes allowing him to recover from normally fatal injuries.
 However, this healing factor comes from his wings; when his wings were removed, he lost this ability.
 His voice is capable of producing sonic frequency beyond the range of human capability as well as creating multiple sounds or voices at once.
Blindfold (Ruth Aldine) is a fictional character, a mutant appearing in American comic books published by Marvel Comics.
 The character is usually depicted as a member of the student body of the Xavier Institute in X-Men-related comic books.
 She first appeared in "Astonishing X-Men", vol.
 3 #7 and was created by Joss Whedon and John Cassaday.

Question: Who in the student body at the Xavier Institute were originally called the Five-in-One?
Answer: Stepford Cuckoos