Queen Lillian makes her debut in Shrek 2. Although initially surprised at Fiona's transformation into an ogre, she is understanding of what has happened and, seeing that her daughter is deeply in love, accepts Shrek into their family. When King Harold is turned back into the Frog King at the end of the film, she still accepts him as she did years ago. She and Harold are a reference to The Frog Prince.
In Shrek the Third, she is widowed after King Harold dies of an illness and she becomes a more determined character, leading the pack of princesses through a series of tunnels in the castle and breaking two walls with her head, whilst humming "My Favorite Things" and "A Spoonful of Sugar" (songs originally sung by Julie Andrews in The Sound of Music and Mary Poppins, respectively). She rallies the other princesses from being damsels in distress to independent fighters.
It is revealed in the film that Fiona inherited her fighting skills from her mother (Lillian asks "Well, you didn't think you got your fighting skills from your father, did you?"). After the film's finale, Lillian is seen in Shrek's swamp home, happily visiting her grandchildren and playing with one of the ogre triplets, who vomits on her dress. At first she looks distressed and a little disgusted, but this changes as she comes to find it adorable.
Lillian is seen briefly in Shrek Forever After in a number of flashbacks, showing her and Harold's decision to visit Rumpelstiltskin to free their daughter from the curse before Shrek saved her. In the alternate universe she and Harold disappear after signing over the kingdom to Rumpelstiltskin. Her last appearance is at the end of the film, celebrating the triplets' birthday.
Decorous and loved by all, Queen Lillian is tolerant of her daughter's decision to marry an ogre if it will make her happy, a thought that initially stands in contrast to her husband's. She seems to be briefly shy and sad after King Harold dies in Shrek the Third and doesn't say much, but after a little while, she perks up and begins accepting life without her husband. This is especially true when she learns that she is going to be a grandmother as Fiona is pregnant and is shown to be very excited. She is determined and nothing means more to her than her family; when they are in trouble, she does everything in her power to save them. Though gentle and nurturing for the most part, if threatened she springs into action and demonstrates her considerable fighting talents.