The Great Saiyaman (グレートサイヤマン; Gureto Saiyaman) is Gohan's
alter ego and an attempt to hide his true identity from his classmates
when he attended school in Satan City. The Great Saiyaman was first born
when Gohan transformed himself into a Super Saiyan in order to disguise
himself as he fought some bank robbers on the morning on his first day
to school. However, his classmates (and in particular, Videl) began to
note strange similarities between himself and the mysterious "Gold
Fighter" (as they described his Super Saiyan form). Concerned that his
identity might be figured out, but wanting to protect the city from
random crime, he approached Bulma and asked her if she could invent a
device that could instantly change his appearance. With his new costume
ready and easily accessible with the press of a button, he could now
protect the city without his identity being easily discovered.
Son Gohan Great Saiyaman Papercraft