Who in the student body at the Xavier Institute were originally called the Five-in-One?
Imperial (comics):  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. Stepford Cuckoos: The Stepford Cuckoos are a set of fictional mutant psychically linked quintuplets (Celeste Cuckoo, Esme Cuckoo, Irma "Mindee" Cuckoo, Phoebe Cuckoo, and Sophie Cuckoo). Stepford Cuckoos:  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.
Stepford Cuckoos