Oscar Hammerstein II went by Ockie.
Oscar Javier Gutierrez II goes by The Bear, Oso, and O.J..
Hammerstein's son jimmy went to school with Sondheim. they became friends and when Sondheim met jimmy's father, they connected. Sondheim didn't know his own father and held his mother in contempt (the feeling was mutual) so the Hammerstein's became like his adoptive family. When Sondheim was a teenager he decided he wanted to go into Oscar Hammerstein's line of work and from then on was mentored in the art of composing and writing lyrics and all other things theatre by Hammerstein.
Oscar Lusth goes by Ozzy.
Oscar Ustari goes by Osky.
Oscar Janiger went by Oz.
Oscar Redman goes by Oz.
Oscar Sainz goes by Oski, and Primu.
Oscar Steer goes by Bunny, and Rabbit.
Oscar Pistorius goes by Blade Runner.
Oscar Goodman goes by Mayor Martini.
Kok Kien Woon Oscar goes by Oscar.
Oscar Jackson goes by Master Fu, and Bandit.