What happens after happily ever after?

Shrek, Fiona, and Donkey set off to Far, Far Away to meet Fiona's mother and father, the Queen and King. But not everyone is happily ever after, as Shrek and the King find it difficult to get along. But when the Fairy Godmother discovers that Fiona has married Shrek instead of her son Prince Charming as King Harold had promised, she plots to destroy their marriage and replace the ogre with her son Charming.