King Harold is the tertiary antagonist turned supporting protagonist in Shrek 2 and a minor character in Shrek the Third and Shrek Forever After. He was Fiona's over-protective father and one of the Fairy Godmother's former henchman, and the King of Far Far Away.
When his daughter Fiona arrives at the castle with her new husband, he is surprised that they are both ogres, he started a fight with Shrek at dinner.
King Harold had secretly made a promise to the Fairy Godmother that her son Prince Charming would marry Fiona. King Harold hires Puss in Boots to assassinate Shrek.
King Harold then succumbs to guilt when Fiona finds out that Shrek is not around. Harold at first refuses when the Fairy Godmother asks him to give the love potion to Fiona that will cause her to fall in love with Prince Charming, because he recoils from this invasion of her free will, but he is forced to acquiesce by some dark threat of disclosure; in the event, when Fiona states that she loved the old Shrek (rather the 'new' one that Prince Charming is pretending to be), Harold swaps the cup which contains the potion for his own.
At the ball toward the end of the film, Harold protects Fiona and Shrek from a blast of magic from Fairy Godmother's wand. He is finally transformed into his original form of the Frog Prince when he is hit by the Fairy Godmother's magic wand. The wife seems not at all unhappy about this turn of events. After this, he apologizes to Shrek and accepts him into the family, his wife saying that he is more of a man for accepting Shrek and Fiona's marriage than he ever was when he was actually human.
Shrek the Third
He tells Shrek on his deathbed that he and Fiona are next in line for the throne of Far Far Away, and Shrek refuses as he cannot imagine an ogre as king. The king dies after telling Shrek about Fiona's cousin Arthur.