She is the only member of the original main cast, who has not appeared in every episode because Alyson Hannigan took leave after giving birth to her first child.

Rebecca had been upset after learning this, but, as a fan of Buffy the Vampire Slayer, was consoled when Alyson Hannigan was cast.

Lily's father, Mickey (Chris Elliott), is an unsuccessful board game creator living in his parents' basement.

Lily is estranged from her father – an absentee parent who she claims "broke my heart every day for 20 years"[6] – until he promises to be there for her following the birth of her son.

She dumped her high school boyfriend, Scooter (David Burtka), on prom night, admitting she only dated him because he looked like Kurt Cobain.

Lily and Marshall grapple with the challenges posed by her credit card bills, especially as they contemplate purchasing an apartment.

This situation forces Marshall to forgo his aspirations of becoming an environmental lawyer and instead accept a position at a large corporate firm.

Despite these sacrifices, they secure the house, only to discover that the neighborhood is in close proximity to a water sewage treatment plant, and their apartment has a crooked floor.

At the end of the night, Lily switches place with Jasmine and dances with much difficulty on stage, eventually falling into the crowd, to Marshall's horror.

[7] In the eighth season, Lily takes a job as an art consultant to a millionaire called "The Captain", who eventually offers to move her to Italy.

Despite initially turning down the promotion due to conflicts with Marshall's job as an environmental lawyer, Lily ultimately decides to accept it.

[30] During the final season, set during the weekend of Barney and Robin's wedding, Lily learns of Marshall's new job, and they get into a huge fight.

[33] The series finale, "Last Forever", reveals that, a few years later, Lily gives birth to a third child, a baby girl whose name is unknown.

In 2014, Alyson Hannigan and Cobie Smulders were also nominated for Favorite TV Gal Pals for their characters Lily Aldrin and Robin Scherbatsky.