He was portrayed by John Colicos from August 10, 1981, to September 18, 1981. Mikkos characterized as one of General Hospital 's greatest villains of all time. In the summer of 2006, it was rumored that the show was considering recasting the role with Daytime legend, Joseph Mascolo; however Mascolo returned to his famous role as Stefano DiMera on NBC'sDays of Our Lives.
Mikkos Cassadine, according to some critics was "The Face of Evil" hell bent on world domination; similar to many comic book super villains in pop culture.
The Cassadine family are were introduced and created by executive producer Gloria Monty. Over the years, Mikkos has been painted as a vicious tyrant, very controlling of all of his children. His personality is similar to that of his widow Helena Cassadine.
Mikkos Cassadine was a Greco-Russian aristocrat. The Cassadine family are descendants of the Russian aristocracy, with connections to the royal Romanov family. They existed for hundreds of years in Russia until the Bolshevik Revolution forced them to flee to Greece. After that period, they built a large economic empire of power and wealth. While his education was never discussed, Mikkos was described as a visionary; a scientific genius whose prowess was displayed fundamentally with his weather control device on Cassadine Island in Greece. His mental pathology of being a megalomaniac and cursed with Cassadine insanity proved his undoing.
Mikkos and wife Helena Cassadine had two children, Stefan and Stavros. He also had an affair with Kristin Bergman, an opera singer, and had two daughters, Natasha and Kristina. Kristin was murdered in front of her daughter Alexis by a jealous Helena. In 2009, Helena revealed that Mikkos had another affair with another unknown woman, and had an illegitimate son named Valentin, who was disowned from birth and was seen as the most unwanted Cassadine.
In 1981, Mikkos made his only on screen appearances on General Hospital when he was the mastermind behind a plot to obtain world domination by holding the world at ransom through the use of a weather machine that could create a severe snowstorm. He claimed it was for a utopia, a perfect world. He never allowed anyone to see his experiments.
He invited several guests, he was questioned by two of his guests Max and Noel who he led into the ice chamber where they froze to death. He claimed they were sent away and died in a plane crash which leads to the deaths of Tony and Alex. He fought with Luke Spencer and died in the freezer. This encounter was the beginning of the long lasting Cassadine-Spencer feud.
In 2016, it's revealed that before Mikkos was killed he revised his will and made sure that all of the Cassadine Estate will be given to the eldest living son. He hid the will from Helena, for he knew she would make sure that their favorite and first-born son Stavros would get the entire estate from his father. After Helena's demise in 2015, the hidden will of Mikkos' Cassadine came to light in 2016 when Mikkos' long lost bastard son Valentin found it in Greece.
Through it and through the final death of Stavros in 2014 and Stefan's death in 2003, Valentin became the only living son and hence sole heir to the Cassadine Empire. As of November 2016, Valentin Cassadine is the CEO of Cassadine Industries.
On May 30, 2018, Alexis is going through Mikkos’ things and looks at a picture of him. She is later wearing a watch he gave his wife that keeps stopping on 10:10.
In August 2019, it was revealed that Mikkos created a codicil for his will which could prove that Valentin is not the rightful heir to the Cassadine Estate and Empire. In January 2020, Valentin was actually revealed to be the son of Helena and an unknown man, who was later revealed to be his brother Victor Cassadine, thus making him Mikkos' stepson and nephew and not the rightful heir.
In April 2021, Alexis remembers a time during a Christmas holiday from her childhood when her father bought her mother a watch. Alexis idolized her father. But she remembers a time she witnessed Mikkos hitting her mother and describes him as a "monster" and she was too powerless to stop him.