PK originally stands for Paperinik. It was the superhero alter-ego of Donald created by writer Guido Martina and artist Giovan Battista Carpi in 1969. Paperinik was a combination of Paperino (Donald Duck's Italian name) and Diabolik, a famous Italian comic-book character.
In the nineties, the character was reworked into a darker, more SF version. While still named Paperinik in Italy, he is also sometimes called Powerduck. Add