Ted Mosby's kids weren't primary figures in How I Met Your Mother but they were crucial to the sitcom's storytelling format, and their names held a lot of significance in the sitcom. Penny and Luke were played by Lyndsy Fonseca and David Henrie for the duration of the series that lasted for the better part of the decade. To keep their appearance consistent, the young actors filmed all of their scenes early on in the show's run.
The teenage versions of Penny and Luke weren't characters in the main timeline of How I Met Your Mother. Instead, they served as the recipients of Ted's story about how he met their mother. The premise of the sitcom centered on Future Ted's long and complicated tale revealing how he met the character who was always referred to as the "Mother." Ted's epic story was the driving force behind the series and as time went on more details regarding the Mother and the kids were unearthed.
The names of Ted's daughter and son were unknown for the majority of How I Met Your Mother's nine-season run. Future Ted referred them both as "kids" during his storytelling but their names were officially revealed in the show's ninth and final season. During the episode "Unpause," a flash-forward scene focused on Ted and the Mother, aka Tracy, at the Farhampton Inn in 2017. Tracy was visibly pregnant and she ended up going into labor. Viewers then learned that Ted and Tracy already had one kid, Penny, and they were about to welcome a son, who they ended up naming Luke. The names of the Mosby kids are more meaningful when taking into account past details within the series.
The Significance Of The Kids' Names In How I Met Your Mother
Penny Mosby was born in 2015 but her name could have very well been a callback to the How I Met Your Mother season 2 episode, "Lucky Penny." Ted missed his flight to get to a job interview because of a court date for when he avoided paying for the subway while in a rush. In a series of flashbacks, Ted tried to explain a series of events that led to missing the flight. He then realized that the chain of events started when he found a penny from 1939, thinking it was extremely valuable. Future Ted then proclaimed that the job he was supposed to interview for would have relocated him to Chicago, meaning he never would have met Tracy. The coin was then referred to as his "lucky penny" and very likely served as the inspiration behind his daughter's name.
The meaning behind Luke's name might be a little more simple. In multiple episodes throughout How I Met Your Mother, Ted shared his love for Star Wars and made it clear that he wanted to name his future kids Luke and Leia. That ended up coming true since he named his son Luke. It's insinuated that the name was based on Luke Skywalker, but it could also be derived from the word "lucky" as in "lucky penny." If so, that old coin may have been more significant than first thought.